Changing Landscapes and Lost Building Arts:

The Evolution of the Early Lowcountry

Charleston Landscape and Lime-based Building

Techniques

By James Liphus Ward and Kalen McNabb

James L. Ward is a Landscape Architect and Assistant Professor of Historic Preservation and Community Planning atthe College of Charleston and Clemson University. He has a record of place making both in Charleston, the larger south eastern US and for the Government of Bermuda. His current research interests include developing more methodical approaches to landscape preservation for both cultural resource planning and interpretation. He teaches history of land design, landscape preservation and design, preservationmethods and assessments, documentation, and cultural landscapes.

Kalen McNabb is a recent graduate of the College of Charleston with a B.S. in Geology and a B.A. in Historic Preservation and Community Planning. His research interests include archival studies and the utilization of systematic lab analysis in preservation and archeological applications.He is currently attending the University of Pennsylvania pursuing a M.S. degree in Historic Preservation with a focuson architectural conservation.

Changing Landscapes and Lost Building Arts:

The Evolution of the Early Lowcountry

Charleston Landscape and Lime-based Building

Techniques

ABSTRACT: This project was undertaken as part of ongoing

research in developing the tools to make more systematic the

study of landscape preservation issues. More specifically

its purpose is to focus attention in the Charleston, SC area

on the larger landscape as it has changed over time. To this

end, I worked with a promising undergraduate student in

combining the interests in his two majors – geology and

preservation. His work provides an important first step in

discussing the geologic basis for the early landscape of

Charleston and the resource context, mostly forgotten, of

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our early building methods and materials. The project,

therefore, is part of a larger and ongoing collaboration of

partners from various community groups and universities

centered on this idea that landscape preservation is a

legitimate field of study that can contribute important

insights in telling the history and informing our future

efforts in preserving the natural and manmade environments.

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“Maybe we are not finding anything because we are not looking for it.” (Jameson)

Introduction:

Since the first settlement of the South Carolina

coastal region in 1670, there have been many changes in

building techniques and materials in response to fire and

storm, available materials and labor as well as stylistic

considerations. When the Lowcountry first was developed,

settlers took advantage of the many local natural resources

to get started. By 1720, many more craftsman and old world

building techniques were imported from Europe and many of

the early efforts were replaced (Wadell, 1-3). Today, many

of these early structures no longer exist and studies

regarding early building techniques must rely on the

archaeology of a few disconnected sites. Moreover, in

recent archaeological studies of early Lowcountry sites,

there has been not only some confusion over the nature of

some early lime-based building materials, particularly

between quarried limestone blocks and a unique coastal

building material known as tabby, but also in a more general

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sense of the utilization of locally available rock limestone

as well as lime putty into a variety of building materials.

Geologically beneath much of the coastal plain, sand

and silt sediments remain in extensive limestone deposits

that formed several thousand years ago. Several

geologically designated formations such as the Santee

Formation and Cooper Marl are known to outcrop along major

rivers within the area. Historical documentation as early

as 1783 details the extent of limestone outcrops along the

Santee River (South Carolina Gazette and General Advertiser,

2). Particularly, there remains much difficulty in finding

limestone outcrops within the area because of the disturbed

nature of the landscape from the late 19th century phosphate

industry (Winberry, 114-116). Tabby - a limestone-like mix

primarily composed of equal proportions of lime, sand,

oyster shell, and water - has been used extensively in the

South since its first use in 1580 in St. Augustine, Florida

(Sickles-Teaves, 19). In many local locations such as

Colonial Fort Dorchester in Summerville , SC, tabby served

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as a relatively quick and competent material to build large

walls (Figure 1).

To date, there remains no definitive studies meant to

determine the among between all early materials options.

There are the beginnings of testing to determine

constituents and finishes for various earlier mortar and

stucco samples (Krotzer). In many sites, however, these

materials are treated the same and thought to originate from

the same source. For example, despite their apparent

similar physical characteristics, tabby and quarried

limestone have dramatically different chemical compositions

which can be determined through chemical and petrographical

analysis. From a historical building methods point of view,

this study seeks to determine the varying chemical and

petrographical compositions of a necessarily limited, but

broadly applicable, set of samples. Thus, the broader and

more contextual goals of this study are as follows:

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1. Perform a literature search regarding the

geology of SC and the historic use of carbonate

materials in the Charleston area;

2. Assemble a broad sampling of carbonate building

materials reflecting its use locally;

3. Determine a chemical composition and analyze the

samples petrographically (microscopically) from

thin sections created from the samples; and

4. Create a link between the diverse fields of

geology and landscape preservation and highlight

the applications of interdisciplinary study in

both these areas.

Project Background

In general, there has been a disregard and confusion of

early building materials and techniques even if these

traditions are still evident in the many built forms of the

area. For example, in Gene Waddell’s important account of

Charleston architecture, he draws conclusions from the

evidence of the earliest engraving (Figures 2, 2a, and 2b).

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The 1739 view is also important for what it does not show. There is little if any evidence of West Indian influence. There must have been little or no influence from the West Indies or it would have manifested itselfbefore 1739. Both the West Indies and Charleston had looked to England for buildings and manners to emulate…Architecture adapted to local conditions is not documented in either place much before 1730, and after this date, the local developments are distinctive (Wadell, 46).

West Indian in this context is referring to buildings and

features built of materials other than wood and brick. Yet

an examination of the enlarged engraving plainly shows

several features that are larger block building material -

both the Granville Bastion and the Half Moon battery. Early

excavations, however, so far have been in other areas and

show only brick walls. There is some written information

which seems to indicate that these features were constructed

of “tabby” and informal references to very early buildings

as “Stone Buildings” (Butler Interview). While the wall was

taken down in the early 1730’s, there exist a few other

buildings within the city of Charleston constructed with

what has been called “Bermuda stone” or “tabby”, including

the Pink House (1712) and the Old Powder Magazine (1713).

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Other early structures were lost especially to the great

fires of 1740 and 1741, presumably removing other signs of

this early building material. Therefore, it is easier to

find evidence and obtain samples from the area outside of

the city.

Survey of Local Use of Limestone

References to Bermuda Stone

The history of the use of Bermuda stone within

Charleston is largely unknown today. Typically, this

material is defined as “a coquina material mined in Bermuda

and some Caribbean islands imported in blocks to colonial

Charleston as a building material” (Poston, 650). One of the

most notable Bermuda stone buildings is known as the “Pink

House” (1712), located at 17 Chalmers Street (Figure 3).

This small two-story structure is said to have been made

completely out of this material. Several other buildings,

including 141 and 141-145 Church Street were constructed

around 1746 and are partially composed of this material.

Currently, most who encounter limestone describe it as a

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“Bermuda Stone” carried on ships as ballast. Even a cursory

visual inspection of the material itself, however, would

seem to dispel this idea. According to those who have lived

and worked in some of these structures, the original Bermuda

stone is known for its lightweight, soft, and porous nature.

Bermuda stone was easily quarried from the bedrock that

compose the island by use of simple tools with saws and

picks. This material was continually imported into the city

as late as 1768 when there is reference to alterations being

done to Granville’s Bastion (Stockton, B5).

Geologically, the stone that outcrops at the surface in

Bermuda is from the Pleistocene Age (2.5 million to 12,000

years BP) and is composed of a sandy calcium carbonate mix

(Rowe, 1). This limestone accumulated through limestone

deposits that were eroded and lithified (compacted) into

Aeolian dunes. The sand that can be found within these

deposits generally range from fine to medium sand. Marine

limestones are rare on the island and are often found in

inaccessible and uninhabited locations. These limestone

deposits provide excellent markers for past sea level rise

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(Rowe, 9). Therefore, it can be hypothesized that the

material known as Bermuda stone is more than likely the

Pleistocene sandy limestone prevalent in the area.

Tabby Usage in the South and Lowcountry

The material known as tabby has had a long and varied

history of usage within the United States and has flourished

in coastal areas because of the availability of the building

materials, strength of construction, and diversity in design

that tabby allowed (Sickles-Taves, 6). This material -

composed of equal proportions of lime, sand, oyster shell,

and water, and first introduced into North America by the

Spanish in their construction of St. Augustine - was used

extensively by the British colonies after 1703. The sand

chosen for the mix was selected carefully as it was required

to be free of all dirt, salt, and major impurities. Recent

grain size distribution studies taken from existing historic

tabby structures show that most samples showed homogeneity

in sand size, shape and color. This helps to support the

theory that the sand was carefully chosen but information

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regarding the exact sources remains scarce (Sickles-Taves,

24). The few references show that pit sand may have been

preferred over channel, beach, and dune sand.

Microscopically, pit sand, or sand deposited on the coastal

plain, is more angular in shape than that continually

influenced by the movement of water. Future studies

regarding limestone and tabby distinction may gain insight

by further focusing on the grain size distribution of the

sand within each sample.

One of the earliest examples of tabby construction

within Charleston is the Old Powder Magazine, constructed

during the early eighteenth century. In the following years

as the colonies within the South grew, the British continued

to use tabby as a building material for their own forts,

including Fort Prince Frederick (1732) in Point Royal, SC,

and Colonial Fort Dorchester (1750-1770) in Summerville, SC

(Sickels-Taves, 20). Today, the largest remnants of both

forts are the thick tabby walls that once enclosed these

spaces. The choice to use tabby at Ft. Dorchester was

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primarily a financial one, as it was a much cheaper method

at the time than bricks and, therefore, unskilled workers

could be hired to build the fort (Bell). During this time

when many private residences were constructed with this

material, a stucco surface coat often was applied over the

thick, yet delicate, tabby walls (Sickels-Taves, 12).

Another reason why tabby was so popular in this area

was due to the unavailability of easily accessible limestone

blocks. The popularity of tabby within the Lowcountry waned

by the beginning of the 19th century, only for usage to peak

again around 1825 in a different form known as Spalding

tabby. This later form is very distinctive since the

original materials such as lime, sand, oyster shell, and

water were changed and now included Portland cement and pre-

made bag lime.

Walls were constructed out of tabby by creating a mold

and then pouring the mixture into the space and allowing it

to harden. For more intricate details, for areas where clay

bricks were unavailable, and for the upper portion of molded

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tabby walls, tabby bricks were created to serve these needs.

Recent studies show that brick use was popular for chimneys

because of its fireproof qualities. Rarely were bricks used

to create an entire structure, although some examples remain

in Georgia (Sickels-Taves, 48).

Another aspect of tabby construction that is pertinent

to this study is the use of tabby as a mortar. Sickles-Taves

and Sheehan (1999) explain that in certain instances, tabby

mortar was used in examples such as Prince William’s Church

(1753) in Sheldon, SC, and Medway Plantation (1696), located

north of Charleston, SC. This mortar was composed of the

usual lime, sand, water, and shell mix except finely crushed

oyster shells and coquina were used to create a putty like

substance. This material has often been referred to as

“oyster shell mortar”; and, according to scholars in the

field, tabby and this material are synonymous in nature

(Sikels-Taves, 49). The extant structures, however, are so

heavily modified by various stucco materials as to make

definitive analysis problematic (Aument).

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Unknown Materials Recovered from Archaeological Sites in

Charleston

In this study of the transition of building materials,

one must rely on archaeology as these early structures no

longer exist. Evidence, however, remains below the ground

in the form of architectural debris and buried foundations.

One such study, from which one of our samples

originates, occurred in September 2008 during an

archaeological survey of McLeod Plantation. This site has

been used as a plantation for over 300 years with the first

settlement beginning in 1695 (Zierden, 11). Documentary

evidence regarding the early settlement of this site remains

scarce, but by the revolutionary war there was an

established plantation with out buildings on the site owned

by Edward Lightwood. Today, the site contains a newer

plantation house, built in 1854, and numerous slave cabins

and outbuildings that were constructed during the 19th

century. During the summer of 2008, archaeological work

focused on a specific building, known as the Dairy.

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Excavation of the soils around the existing building

revealed a brick foundation that was supported by a lower

level of what is referred to as “Bermuda stone” (Figure 4).

At this particular area, the stone is irregular and its base

is found 1.2 feet below the surface. Cream ware and other

artifacts found in the same horizon as the Bermuda stone

support a late eighteenth century or early 19th century

date. According to the Charleston Museum’s archeologist,

Martha Zierden, in 2008, the Bermuda stone foundation was

unexpected and that an estimated construction date for this

building is around 1780, and therefore part of the Lightwood

occupation period. The Bermuda stone foundation more than

likely predates the dairy and either is a remnant foundation

or the stone was recycled from a previous use on the site.

Nevertheless, it is apparent that at this site the stone

being referred to as Bermuda stone was used as an early

building material. In establishing a source for this stone,

however, it is unfortunate that virtually all of the native

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limestone outcroppings were heavily disturbed by mining

operations.

Characterization of the Landscape in the Low Country Prior

to Phosphate Mining

Historically, the phosphate region within SC was found

along the coast in Oligocene to Pleistocene deposits

extending seventy miles from the Wando River in the north to

the Broad River in the south (Malde, 2-6). These phosphate

deposits were generally found parallel to the shore and from

ten to thirty miles inland from the coast (Chazel, 1-2).

Figure 5 shows the extent of mining operations in the entire

area as well as references to the various companies. These

beds were not continuous in nature and as a result of this

several different phosphate localities existed. The Wando,

Cooper, Ashley, and Edisto Rivers’ subdivisions were known

outcrops. Specifically, the Wando River phosphate was known

for its fossiliferous content and therefore was often not

successfully mined. The Cooper River beds as late as 1904

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“have not proven remunerative” and despite the good quality

of the phosphate found, there was not a large enough

quantity to justify exploitation (Chazel, 3). Northeastern

Railroad and Mount Holly beds were known for their high

quality and large number of individual beds. Mining in this

area required the use of blasting and the rock in this

locality was known for its light brown color. Lighter

grades of phosphate found here, however, generally were

lighter in color, including rocks near Ten-Mile Hill

(currently near the Charleston Air Force Base on the north

bank of the Ashley River), which “is a very light colored

rock, which is so soft and friable that it suffers great

loss when handled by ordinary methods” (Chazel, 3).

Despite the number of outcrops in the Charleston area,

none compared to the Ashley River beds. In this location,

deposits were mined on the surface on both sides of the

river for ten miles from Bee’s Ferry to the Ashley Works.

Generally the upper portion of the deposit was known for its

insufficient quality but below this deposit, which still

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could be found on the surface, high grade phosphate rock was

present in large quantities. By 1904, these beds were the

sole source of land rock mining. These beds were known to

vary in hardness and color but early chemical analysis

showed these beds were high in iron and aluminum (Chazel,

4).

In the late 19th century, chemical analysis was

performed on several rocks to determine whether the chemical

composition of the phosphatic rock varied as much as the

physical characteristics did. These studies showed that

average sample of rock contained 25% to 28% phosphoric acid,

2.5% to 5% carbonic acid, 35% to 42% lime, 4% to 12%

insoluble silica, with smaller percentages of other elements

such as fluorine, magnesium, aluminum, iron and organic

matter containing nitrogen (Chazel, 10). From several other

historical studies, it was apparent that Carolina rock, as

it is often referred to, was known for higher amounts of

organic content ranging from 2% to 6%.

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The extent and quantity of the deposits prevalent prior

to the phosphate mining may never be known because of the

lack of previous study before the industry began. By

looking at the geology and areas of heavy mining, however,

it is possible to make some inferences regarding the extent

of these deposits. Publications regarding the industry and

deposits within the area state that the beds were generally

horizontal in nature, showing little to no deformational

processes had affected the beds. The normal stratigraphy

(layering) of these deposits found specifically on land by

those mining the area were known for a surface soil varying

from a few inches to a foot, overlaying deposits of lighter

colored clay with iron nodules and little to no calcareous

matter. Below this layer in some places occurred a blue

clayey marl with shell fragments with a thickness of two

feet, which was above a layer of coarse sand no more than

one to three inches in thickness. The term marl has been

indiscriminately used by early geologists to describe

materials composed of lime that today include limestone,

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greensand, and loose shell (Malde, 10). These layers

overlaid phosphatic nodules in a blue to buff colored marl

which transitioned into highly phosphatic marl and a

silacaeous marl (Chazel, 19-20). River deposits also

featured a variety of beds where phosphate deposits were

located including gray marl, a white hard marl, a green

sand, and other hard marls which contained little to no

phosphate.

This interest in phosphate mining within the Lowcountry

began as early as 1842 when Edmund Ruffin created an

agricultural survey to detail the extent of the limestone

and marl deposits within SC. During his examination along

the Ashley River he detailed the occurrence of hard lumps

and a large amount of shell fossils (Chazel, 34). Following

this Professor M. Tuomney finished the project where he

describes the Ashley beds:

In ascending the Ashley, from Charleston, marl is first seen at Bee’s Ferry, on both sides of the river, below high water level, both here and elsewhere, on theriver, it is exceedingly uniform in structure and internal appearance, with the exception of about two or

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three feet of the surface, which is composed of irregular and waterworn fragments of marl stone, embedded in clay, and containing numerous fossils in the state of casts. These fragments are scattered overthe surface, so as, in some places, to offer obstruction the cultivation of the land. On examining these fragments, and at Drayton Hall, they have been gathered from the lawn and thrown in heaps (Chazel, 35).

In the following year there were more discoveries and

studies performed regarding this rock but mining did not

begin until after the Civil War when in 1867, the

Charleston, S.C. Mining and Manufacturing Company was

formed and started mining on the Ashley River. Quickly,

several companies formed to mine this lucrative material and

by 1871, 17,655 tons of phosphate was being shipped. By

1893, this number peaked at 249,339 tons and by 1894, a

total of 3,123,550 tons of Carolina rock had been shipped

(Chazel, 55).

Geologically, the marl that Tuomey referred to is known

as the Cooper Marl, which is Oligocene in age and outcrops

along major rivers and extends inland twenty miles from the

Ashley River. The Oligocene Cooper Marl is the oldest

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formation exposed, containing soft fine-grained, impure

carbonate that overlays the Eocene Castle Hayne formation

limestone generally at 293 feet below sea level, giving a

thickness of the Cooper Marl to be 275 feet thick. The

outcrops form massive river bluffs that are yellow and

hardened above river level but soft with a dark green or

blank film at the river level. Despite the historical use

of the umbrella term “marl” to describe this material, the

Cooper Marl is ultimately a consolidated, fine grained

carbonate deposit (Malde). The carbonates within this layer

are composed mainly of calcite with some dolomite with minor

constituents being sand, clay, phosphate, and water. Above

this the lower Miocene is generally absent from the

stratigraphy, with the exception of a one foot bed located

thirty miles from Charleston. This deposit is primarily

composed of a hard limestone. The middle Miocene Hawthorn

formation is composed of phosphatic sand and crops out along

the Savannah River but is not apparent in Charleston. The

upper Miocene Dublin formation, which is composed of ten

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feet of coquina, crops out along the Cooper River.

Pleistocene marine deposits can be found nearly everywhere

within the Charleston area. The oldest Pleistocene

formation, the Ladson formation, is composed of sands with

phosphate deposits that dip generally toward the sea. In

localities along the Ashley and Cooper Rivers, however,

Pleistocene Ladson formation overlaying this Oligocene

deposit makes for some inconsistency. The Ladson formation

is geologically known as the source of many of the

phosphatic outcrops as mentioned in the historic references

discussed previously. This deposit, however, contains many

conglomerate and sand deposits along the phosphate nodules.

Therefore, geologically speaking, the phosphate rock is

Cooper Marl that has been phosphatized and reworked into the

bottom part of the Ladson formation (Malde, 1-3).

Therefore, inferences from Tuomey’s statement and the

geology of the area can be made regarding the possibility of

an early limestone, perhaps the Cooper Marl, being used as

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an early building material. Despite the fact that in many

locations, the natural stratigraphy has been disturbed due

to the extensive mining in the late 19th and early 20th

centuries, it is apparent that a marl of some sort

outcropped in many locations along the Ashley River during

the settlement of the area. This statement also provides

insight to the fact that this marl was readily available and

possibly could have been used for construction of early

buildings. Figure 6 indicates the basic geology of SC,

reflecting the combination of circumstances including

topography along the rivers which reveal the underlying

bedrock. The presence of both Santee Limestone as well as

Cooper Marl was and still is quite significant.

Samples and Visual Characteristics:

Samples were collected from several different sources

that are of particular interest to this study. Within the

scope and time limitations of a short term study effort, the

intent is as follows:

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1. to develop a broad sampling as a preliminary attempt to

verify that there was some kind of use of the limestone

based building from the beginning to contemporary

times,

2. to establish that there is the distinct possibility

that native limestone, not just Bermuda stone, was a

part of the early buildings of the area, and

3. to see the evolution of building methods and materials

as a response to the changing landscape.

Figure 5 illustrates the larger area around Charleston

and also indicates the regional context highlighting the

extent of late 19th and 20th century phosphate mining in the

area. Based on aerial photos of vegetation clearing done in

the early 20th century, however, additional research in

defining the extent of disturbance from mining is underway

which will offer a more finely detailed idea but is not part

of this study. This effort would assist in future sampling

to allow researchers to focus on areas that were not

disturbed.

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Bermuda limestone was sampled directly from the country

and is pivotal to this study, as much of this material was

purported to have been exported to the English colonies

during the eighteenth century. I basically picked this

sample up from a friend’s garden setting. It showed an

uneven texture overall without saw marks and with traces of

pitting on the surface indicative of recent stones that have

been fairly recently exposed to “acid” rain similar to stone

found both along the ocean and in relatively undisturbed,

exposed sections of bedrock. Based on on-site observations,

many of the sites of early limestone excavations occurred

along the accessible shoreline. This stone is rough in

nature and is dense to the touch although still workable

with hand tools (Figure 7). In fact, much of the limestone

encountered in various archeology digs is simply classified

as “Bermuda Stone” with the justification that there were

some historical records that the material was brought over

as ballast. Considerably more research, however, into the

extent of this trade in stone needs to be documented.

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A sample of local limestone taken from the Giant Cement

Company mine was also studied so that it may be compared

with the chemical analysis of other building materials. It

is soft and able to be cut easily with simple tools such as

a hand saw. This was material left on the surface in the

open mining pit, originally a slurry and hardened with

weathering (Figure 8) Several other samples that were

studied visually but not chemically included a piece of

Santee limestone examined by the student co-author during

the Fall of 2008. It was in Hardeeville near where the Giant

Cement mine is currently. It was noted as quite full of

fossils and harder than these samples. It also was

characterized with small and larger fossils heavily

cemented.

Two samples of unknown composition were collected from

an archaeological dig at Drayton Hall located along the

Ashley River in Charleston, SC. This dig is ongoing and the

work has not been officially completed but early indications

are that it is from a previously unknown section dating from

backfill and an early wall and house foundation of

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approximately 1685 and predating the current house of 1735

(Hudgins Interview). These samples, labeled as “hard sample”

and “soft sample” are very different when compared to one

another. The hard sample exhibits a white and brown colored

exterior. It is very dense to the touch and much heavier

than the soft sample. The unknown soft sample is brittle and

light when held (Figure 9 and 10).

Another archaeological sample was collected from a dig

done at McLeod plantation located on James Island, SC by the

Charleston Museum as part of a College of Charleston field

school two years ago (Zierden, 9). This sample is rough and

particles of sand and/or carbonate easily are removed when

lightly brushed. Its location in the foundation of a

relatively later structure would seem to indicate its reuse

from elsewhere (Figure 11).

Several pieces of brick from the foundation wall of a

private residence in Charleston at 97 Rutledge Avenue were

also of interest, as they are purported to have been made

out of a mix of sand and marl and are very light in color

(Figure 12). This structure was built during 1886 during a

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time when limestone marl also know as argillaceous lime (15-

25% clay and 75-85% CaCO3) or calcareous marl (25-35% Clay

and 65-75% CaCO3) was being used for the creation of bricks

(Stockton, personal communication). It was also a period of

time when the phosphate industry was beginning mining

operations in Charleston. In fact, the house where it was

sampled was owned at the time by a phosphate mine owner. So

far, only anecdotal research has documented this effort.

Given the current proximity in the field between the

limestone rock and phosphate deposits, this historical

collaboration of industries seems worth exploring further.

Two other samples from an original plantation building

foundation at the Horry-Lucas House (date undetermined, late

eighteenth century is a conservative guess) located at

Charlestowne Landing, a state park on the site of and

interpreting the earliest English settlement from 1670, were

also studied visually as one appeared to be an actual stone

and another appeared to be a mortar made from limestone as

evidenced by the color and location where the sample was

taken (Figure 13 and 14). Both samples occurred within the

30

enclosed area that makes up the foundation of the entry

stairs of the structure. Additional sampling and testing

from this site will reveal more as recently new lime and

oyster shell floors have been revealed just this year.

Interestingly, the headline of the newspaper story

characterizes this floor material as “tabby”, a commonly

recognized early material but a characterization that is

problematic to this study (Behre, 2B).

A simple visual inspection highlights the problem of

misinterpretation of original building material. In this

case, the open grain texture of the samples from McLeod and

Charlestowne Landing would appear to be similar. The dense

consolidated stone from one of Drayton samples appear

unique. The samples from Bermuda are entirely different in

being more moderately consolidated and pitted from reaction

to rain. The very fine and crumbling samples both from the

mining operations in Giant cement and the second sample from

Drayton appear reasonably similar. As the chemical analysis

would reveal, simply resting on visual cues can lead to an

erroneous classification. Subsequent petrographic analysis

31

of thin sections helps to see the material as a whole more

clearly to describe its compounds as well as its elements.

Chemical Data

Utilizing accepted laboratory methodologies,

distinctive chemical fingerprints were found for each

individual sample and specific elements were focused upon to

determine if a chemical fingerprint was possible (EPA). Rare

earth elements (REE) were specifically focused upon as they

are considered good indicators of original depositional

environment and the concentrations are unique for each

individual site (Bellanca, 141-2). REE have been

specifically focused upon in recent geologic studies in

order to source marine sediments and as a tracker for paleo

reduction conditions as the element behaves differently than

other rare earth elements (Bellanca, 142). Geologically,

limestone tends to be lower in REE than other materials such

as clay and heavy minerals. For many limestones, sea water

is the greatest source of these rare elements. It is

32

apparent from the sources sampled that each sample has its

own chemical fingerprint, and no correlation between known

and unknown samples could be reached at this time. It is

possible that with a larger number of unique samples and

further testing that this can be accomplished.

Principal Component Analysis performed on the samples

illustrated interesting trends within the data set. Plotting

the principal components of each sample, it is apparent that

samples from the same source rock plotted similarly

together. Both the Giant Cement core and the 97 Rutledge

Brick plotted differently than the other samples. Strong

similarities were shown among the McLeod, Drayton Hall Soft,

and Bermuda Limestone samples showing it is possible they

originated from the same source. When looking more closely

at the elemental data, however, it appears that there are

some differences among these three. For example, the Drayton

Hall Soft sample has much higher values of magnesium, iron

and silica.

The 97 Rutledge brick showed high concentrations of

most major elements, including large concentrations of

33

silica. More than likely during the creation of this brick,

a combination of limestone and sand was used for the

original mix. This is supported by the fact that sand grains

can be seen visually within the original sample. The brick

also displayed higher concentrations of REEs than any other

sample. This is because many different kinds of materials,

such as sand, limestone, and clay, were used to create the

individual bricks, and as a result, chemical analysis has

detected high concentrations of many different elements.

One of the most surprising findings is from the

analysis of the Drayton Hall Hard sample. Tests showed that

this sample is high in iron and, surprisingly, uranium.

Uranium values were observed to be the highest in these

samples, along with vanadium and chromium. It is likely that

this sample either formed in very different conditions than

the other samples or was extensively altered during post

depositional weathering. In any case, uranium exposure was

part of the phosphate mining experience and may be what one

is seeing here.

34

Out of all of the samples tested using the inductively

coupled plasma/mass spectrometry (ICP-MS), the samples with

the greatest similarities are the stone from Bermuda,

McLeod, and the Drayton Hall Soft sample (Figure 15).

Chemical variability exists within all of the data, but for

the most part their chemical concentrations are similar.

Further microscopic analysis should help reveal the

structure and the chemical compounds that at the heart of

this study. One of the few differences detected, for

example, is the concentration of silica and magnesium within

each sample. The Bermuda stone exhibits low concentrations

of silica and magnesium while the Drayton Hall silica

concentrations are much higher. Also, according to tests,

the Bermuda stone generally displays higher concentrations

of REE. Therefore, it is possible that this sample is from

Bermuda, but could have been formed in a different location

with a much larger input of sand. Bermuda geology is known

for both its marine and eolian (wind-blown) limestone

formations. A further petrographic analysis reveals that the

35

sand was likely synthetically mixed but its constituent

analysis may be revealing its source.

Imaging Methods

Imaging methods, or petrographic analysis, use direct

observation of a material sample and various microscopic

analyses. The material is examined both as a sample and,

where possible, based on where it is located. Then, thin

sections are milled to transparency and placed on slides for

examination. In this case, the type of microscopic analysis

chosen was polarized light microscopy (PLM) which allows one

“to qualitatively identify components, examine textural

relationships, and inform further instrumental analysis”

(Neese in Krotzer, 44). By combining thin section visual

analysis of a sample with an understanding of its location

as well as acid reduction testing to identify constituent

components, one may best surmise the materials and perhaps

its origins. These thin sections, where available, are shown

immediately next to the photograph of the sample. The

authors were assisted with this petrographic portion of the

36

analysis by various members of the local University Geology

Department.

The Bermuda limestone sample (Figure 7b) is

characterized by forans and red algae remnants as well as

lagoonal facies. Its overall texture is relatively open with

a type of chrystalline binding structure in evidence between

the major components. This is a typical limestone structure

that continues to bind and consolidate over time hardening

the material.

The Giant Cement sample was not suitable for thin

sections as it turns to virtual sand upon cutting. The two

samples from Drayton Hall – hard and soft – were very

different. The soft sample (Figure 10b) could be

characterized as a synthetic mix with larger aggregate

pieces but much more consolidated and uniform. The hard

sample (Figure 10a) was immediately evident from its basic

structure as not primarily limestone but phosphatic rock

with numerous forans. Forans (or Foraminifers) are a large

group of amoeboids that tend to produce shells with one of

multiple chambers made of calcium carbonate (CaCO3). These

37

shells are generally small but one may see examples of much

larger pieces. Phosphate is itself a sedimentary rock

generally a minimum of twenty percent phosphorous. This

sample was also considerably denser than the limestone

samples. It tends to form in deeper waters and is,

therefore, another marine rock but it is not likely to be

stratigraphically close to limestone except in locations

subject to heavy erosion such as along the river banks.

The McLeod sample (Figure 11a) also has forans but with

a more pronounced geopetal structure (caves with cement

forming). One also sees red algae, pieces of bivalve and

worm tubes mixed in. Although not nearly so dense as Bermuda

stone, it shows many of the same visual characteristics.

The sample from 97 Rutledge (Figure 12a) is quartz

cemented by calcite. The angular aspect of the aggregate

indicates an inland quarried sand source. Its uniformity

also is an attribute of its manufacturing. If the calcium

carbonate came from the Cooper marl as circumstantial

evidence seems to indicate, there would have been some

additional processing to maintain its consistency. It was

38

not a straightforward mixing process. Further additional

research is needed on sources and methods of manufacture in

order to evaluate this material.

The samples from the Horry-Lucas House at Charles Towne

Landing (Figure 13a) were very similar to the Bermuda stone

both in its constituents but also in its general texture.

Its density tended to be more open, less consolidated. Given

the variability of limestone in Bermuda, it could have come

from there, perhaps from an upland source protected from

elements and not compressed. Further testing would be in

order especially in this instance.

The use of PLM, therefore, proves highly instructive

when analyzing these materials. Together with the REE

analysis a more definitive statement can be made as to

composition as well as origin. It is, however, imprecise and

dependent on a level of field experience and review of many

more samples to achieve reliable results.

Conclusion

39

Even with the limited sample set, the question posed by

this project has been addressed. Limestone was very much a

part of the early building traditions in various forms.

During the 18th and 19th centuries in Charleston, there were

many instances of tabby, limestone, and a hybrid tabby-

limestone construction in many different forms. Geological

research highlights the possibility that prior to phosphate

mining, limestone in the form of the Cooper Marl did outcrop

at the surface near all the major Lowcountry rivers. There

is, however, uncertainty regarding whether the Cooper Marl

was an adequate building material or more than likely

unconsolidated and better suited for a slurry mix.

This research has shown that there were many materials

used during the history of early Charleston that could

possibly be mistaken as the “Bermuda stone” imported from

the island. Early interpretations have said the “Bermuda

Stone is identical with the Coquina stone used in building

by the Spaniards of St. Augustine” (Smith, 344). Naming

unknown materials as such effectively hides information that

may prove valuable to many archaeologists, preservationists

40

and even geologists. It is apparent, however, through the

archaeology of early Charleston sites, that limestone to

some extent was being used as major constituents of stucco

and mortar. This fact helps validate the assumption that

early builders and Old World craftsmen not only brought

techniques native to their homeland to this area but also

had knowledge of local natural resources and chose to use

these materials extensively.

Thin section analysis reveals great similarities

between all the limestone samples; however, the density of

the material itself varies greatly. Chemically, it appears

that the Bermuda limestone and the local McLeod limestone

were the most similar in composition. The Drayton Hall soft

sample was stlightly removed from these two in the chart,

perhaps indicating that the constituents of this material

were imported from Bermuda even if there had been local

processing. The hard Drayton Hall sample plotted fairly

inconsistently and only somewhat similar to the other two,

but this may just reflect the chemical similarities in

different sources for limestone in general. Analyzing for

41

phosphorous would have undoubtedly made the analysis

clearer.

Recommendations for Future Work

Expanding our awareness of native building materials

has many applications within the fields of historic

preservation, archaeology, and geology. It is essential,

however, that further study be performed to obtain a more

complete picture of adapted native building methods.

Comparative samples of oyster shells should be analyzed as

they were used as constituents for mortar and stucco as well

as rock limestone. In addition, it is recommended that

sampling of existing limestone outcrops along the Lowcountry

rivers be conducted to see if representative samples can be

obtained. In addition, it is likely, however, that much of

this material has been disturbed or altered in some ways

because of the extensive mining recorded in the area.

Developing a GIS based system of overlaying recently made

available old timber land maps (formerly phosphate mines)

onto current aerials should offer likely locations for field

42

studies. This level of analysis would also prove useful in

describing the relatively recent changes which have so

drastically altered the landscape of the Lowcountry.

It seems that this information should be an important

part of the materials research at contemporary archeological

excavations. Large stone limestone and phosphate stones are

being uncovered at the National Trust’s Drayton Hall right

now which should prove interesting to examine in light of

these initial studies (Figure 16). Excavations at

Charlestowne Landing are showing a more varied use of the

lime material that the first settlers utilized. Excavations

at Fort Dorchester are partially completed showing a rich

history in the use of tabby walls and limestone mortar.

Also, it is essential to note that the extensive mining

along the Ashley River not only altered the geology of this

area but the flora as well. Casual observation has indicated

the return of natural flora after an absence of over 100

years in places like Long Savannah which is recently been

included as part of an additional 38,000 acres added to the

Ashley River Historic District as the working part of the

43

plantations such as Drayton Hall. It is, therefore, timely

to bring forward the notion of a reemerging natural

landscape and might prove useful to those in charge of

managing those natural and cultural resources.

Also, a more extensive literature and field search is

needed to determine if it is possible to find further

reference to the early construction lime-based methods such

as “mud walls”, “spaterdash” (known locally as “splatter

dash”) stucco finishes (McAlester, 41), and even the

utilization of crumbled rock as part of natural cement

mortars and stuccoes. This project is multidisciplinary in

its application and requires greater emphasis on time and

resources to determine the development of early limestone

building methods and materials in the greater Lowcountry

area.

Finally, this study may be most useful as a starting

point to facilitate an ongoing collaboration of landscape

preservationists and geologists in fieldwork, laboratory

analysis, and documentary research. Where significant mining

activities have occurred, such as along the Lowcountry

44

rivers, an understanding of the historical landscape and of

the early building methods requires such a collaboration.

Such an understanding aids not only our efforts at

reconstructing historic fabric but also efforts to utilize

local building materials in new construction. The two

perspectives – one very object and laboratory oriented and

the other looking for relationships with the broader

cultural landscape – should make for a dynamic approach and

discussion.

45

Figure 1: Tabby Walls of Ft. Dorchester (Bell, 1)

46

Figure 2: “Charles-Town the Metropolis of the Province of SouthCarolina…” from a painting by B. Roberts shows the earliest

version of entire waterfront in Charleston.

Figure 2a: Detail of Granville Bastion highlights what appearsto be different materials used on the defensive wall (Source:

Wadell, Illustration 50A)

47

Figure 2b: Detail of Half Moon Battery also appears to be adifferent material (Source: Wadell, Illustration 52A)

Figure 3: The Pink House (photo by author)

48

Figure 4: Stone Recovered from McLeod Plantation in situ

(Source: Zierden, 93)

49

50

Figure 5: Map of the Phosphatic Deposits of South Carolina(Source: Charleston Museum in Shuler,14)

51

Figure 6: Geology of South Carolina (Source: Heron, pp.5-6)

52

Figure 7and 7a: Bermuda Stone sample with thin section PLM

(Photos by author)

53

Figure 8: Core from Giant Cement (Photos by author)

Figure 9 and 9a: Drayton Hall Hard Sample and thin section

PLM (Photos by author)

54

Figure 10 and 10a: Drayton Hall Soft Sample and thin section

PLM (Photos by author)

55

Figure 11 and, 11a: McLeod “Bermuda Stone” and thin section

PLM (Photos by author)

56

57

Figure 12 and 12a: 97 Rutledge Brick and thin section PLM

(photo by author)

Figure 13 and 13a: Charlestowne Landing sample and thin

section PLM (photo by author)

58

Figure 14: location of sample in foundation wall (Photo by

author)

Figure 15 Principal Component Analysis of Samples Sourced(Figure by author)

Principal Component Analysis

-3-2.5-2

-1.5-1

-0.50

0.51

1.5

-9 -7 -5 -3 -1 1

Pc1

Pc2

97 Rut 197 Rut 297 Rut 3McLeod 1McLeod 2McLeod 3Bermuda 1Bermuda 2Bermuda 3DH Soft 1DH Soft 2DH Soft 3DH Hard 1DH Hard 2DH Hard 3Core 1Core 2

59

Figure 16: New samples being excavated at Drayton Hall to bestudied as early building material (Photo by author)

60

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