Journal of Archaeological Science (2003) 30, 227–238doi:10.1006/jasc.2002.0829

Roman Wheel-cut Engraving, Dyeing and PaintingMicroquartz Gemstones

Amnon Rosenfeld and Michael Dvorachek

The Geological Survey of Israel, 30 Malkhe Israel St, Jerusalem 95501, Israel

Shua Amorai-Stark

Art Department, Kaye College of Education, 136 Yehuda Halevi St, Be’er-Sheva, Israel

(Received 24 May 2001, revised manuscript accepted 5 March 2002)

Remnants of materials used during the engraving process of eight hard microquartz gemstones from the EasternRoman Empire were investigated. This random case study reveals that engravings were made by a rotational lathe ofbronze and iron drill-wheels using abrasive materials. Found in the engraved grooves were grains of the tin, lead andbarite lubricant agents that held the abrasives facilitating the engraving and polishing process. Iron-oxide was used forpainting the gemstones dark colours by bonding with bone glue in a heat process. Calcium carbonate was used inwhitening carnelian by controlled heat treatment. Substantial silver and gold particles were observed within the groovesindicating their decoration purposes, by emphasizing the engraved motif. � 2002 Elsevier Science Ltd. All rights reserved.

Keywords: GEMSTONES, ENGRAVINGS, MICROQUARTZ, ROMAN PERIOD, CHEMICAL ANALYSIS,ABRASIVES, LUBRICANT AGENTS, DYEING, PAINTING

Introduction

T he present work attempts to trace the tech-niques of the Roman lapidary craftsmenengaged in engraving hard gemstones. The hard

gemstones (hardness 6·5–7 in Mohs’ scale) usuallybelong to the quartz group, which includes the quartzand amethyst as macro-crystals, and the microquartzgroup, which includes carnelian, agate, onyx and jaspermade of multi-microcrystalline quartz (Sax, 1996).These hard engraved gemstones were much appreci-ated during the ancient period, and used as an object ofvirtue. Stones of greater hardness like garnet, sapphireand ruby were also worked at this time as gemstones,but are not included in this research.

Literary evidence shows that sometimes Romanintaglios were used as seals, which had official andpolitical functions. During the Late Roman period,engraved quartz and microquartz gemstones were usedmore for jewellery and/or as amulets, rather than asseals. They were common fashionable decorativeobjects, blessing the wearers with protective powers aswell as beautifying them. Both the stone and theengravings were believed to bring good luck and pros-perity to its owner. A person who wore a gemstoneengraved with Zeus or Fortuna, might feel doublyassured by the magical stone power and by theengraved deity. Magical properties such as curing

2270305–4403/03/$-see front matter

specific diseases, ensuring success or guarding againstthe evil eye were attributed to certain gemstones(Scarborough & Nutton, 1986: Pliny, 36, 37).

During the Roman period engraved gemstones wereusually mounted in bronze, iron, silver or gold fingerrings. They were mounted also in necklaces, pendants,brooches and earrings (Henig, 1988, 1997). Theengraving motif is related to the colour of the gem-stone. Helios was frequently cut on red-orange blood-stones and carnelian, while Demeter on green hardstones such as jasper or chrysoprase. Black onyx andhaematite were preferred for magical amulets (Henig,1997). Most of the amulets were cut in the positive,whereas the ring-stones that were cut in the negative,used as seals and made to be seen in the impression.

Gem-cutting was fashionable throughout theRoman Empire especially during the 2nd–3rd century (Henig, 1997). During these periods engraved gem-stones were manufactured for mass consumption byworkshops located in the cities. During the LateRoman and Early Byzantine periods the production ofengraved gemstones decreased. From the 3rd to the 6thcentury the Sassanian Empire produced very largenumbers of engraved hard gemstones in official andlocal workshops for sealing and decoration.

The engraving wheel-cut technique was similar totoday’s lap-wheel/drill cutting technique. The actualcutting was done by rotating drills (of various widths

� 2002 Elsevier Science Ltd. All rights reserved.

228 A. Rosenfeld et al.

and shapes-pointed, spherical, or lap-wheels mountedon spindles) using a horizontal fixed lathe moved by abow strap rotated manually, or by water flow. Anillustration drawn on a tombstone of a Roman gemengraver (Boardmann, 1970; Ogden, 1982) proves theexistence of this technique. The manual bow drill wasused much earlier, as manifested in an Egyptian wallpainting from c. 2000 (Gorelick & Gwinnett,1981). Two elements were, and still are, important fora successful engraving—an abrasive powder and alubricant material to smooth the friction on engraving.The availability of emery (=corundum, aluminaAl2O3-hardness around 9 in Mohs’ scale) as abrasivematerial (Heimpel et al., 1988; Sax et al., 1998) andbronze drill or wheel (Gwinnet & Gorelick, 1987; Sax& Meeks, 1995) enabled one to engrave in hardergemstones. Both bronze and iron drills/wheels wereused for engraving. The iron drills were probably madeof steel with carbon (0·5–1%), which could reachhardness of about 7·0–7·5. The bow lathe could berotated about 850 rpm (Gorelich & Gwinnett, 1981),while the gemstone is held directly on the drill/ wheelwith the fingers or cemented to a ‘‘dop’’. Holding thegemstone in the hand, moving it against the revolvingdrill, gave more artistic flexibility, enabling engraving acurved line. The abrasive powders rubbed into thestone create the engraving cut, resulting in parallelgrooves. Diamond (probably from India) and emery(from Naxos Island) were used as abrasives by theGreek and Roman engravers (Scarborough & Nutton,1986: Pliny, 36, 37; Ogden, 1982). Many blocks ofemery were excavated from a Late Bronze Age site inSyria (Bordreuil et al., 1984). This find indicates thatthe ancient engravers knew about emery as anabrasive-material already at a very early stage.

Usually lubricants—cooling agents such as water, oilor waxy pastes—were and are used to lessen the heatproduced during the engraving between the stone andthe wheel. In addition, the lubricants function as aholding medium for the abrasives, partly preventingtheir scattering. An Egyptian wall picture from Sakka-rah (Gorelick & Gwinnett, 1981, Figure 8a), depicts asitting seal-maker/engraver using a hand drill with hisstanding helper, both holding and squeezing a leatherpouch under their arms, probably feeding abrasive andliquid materials to facilitate the engraving.

Engraved gems from a properly excavated, well-dated archaeological context are rather rare. Most ofthe known engraved gemstones were found on thegrounds of ancient settlement sites, frequently on bathsites. (e.g. Hamburger, 1968; Zienkiewicz, 1986). Thereare many catalogues of private and museum collec-tions, purchased in the antiquities markets or auctionhouses, that describe gems, but have no stratificationor geographical information.

We present here a case study of eight carnelian andagate gemstone intaglios, randomly chosen from aprivate collection. They were most probably producedin the cities of Israel for mass consumption during the

Roman period from the 1st to the 4th centuries (including one Sassanian gemstone). They are said tohave been found in the Judea Mountains and the JudeaDesert areas, and were sold in the Jerusalem antiquitiesmarket. Knowing the market, they could well havecome from anywhere in Israel, Jordan or the surround-ing areas—the eastern part of the Roman Empire.These are common Roman pieces, similar to the gem-stones found in collections from sites in Israel (e.g.,Caesarea: Hamburger; 1968; Amorai-Stark, 1999) orJordan (e.g. Gadara: Henig & Whiting, 1987).

Hard gemstones have excellent durability and arewell preserved in the ground, thus, making themappropriate for chemical analysis that might detect thematerials used during the engraving processes. Thiswas made possible by a Jeol-840 scanning electronmicroscope (SEM) (in the Geological Survey of Israel),equipped with a back scattered electron detector (BSE)and a Link-10000 energy dispersive system that iden-tify and measure the different elements in a non-destructive way. The gemstones were carbon coated forSEM and EDS examinations. The remains of thematerial found within the engravings, were not suffi-cient for XRD powder analysis. All SEM micro-photographs were made directly from the engravingsmarks themselves after carbon coating without anytreatment (Pl. 1–5). The main object was to trace theancient engraving methods and to detect the materialsused for the engraving process.

The Studied Gemstones and their ChemicalResultsLike most of the Roman intaglios, the investigatedspecimens in our study were engraved by a variety ofdrills in the wheel-cut technique. They represent atypical spectrum of the Roman iconographical motif,style and engraving techniques. All the gemstones canbe assigned to one of the stylistic-technical groupdescribed by Maaskant-Kleibrink (1978), and Henig(1988). They also represent typical Roman gemstoneshapes, that are mainly oval, flat or cabochon types(classification after Amorai-Stark, 1993: 12), withcommon sizes between 5–20 mm. The followingmicroquartz gemstones were investigated:

No. 1–197—Type C3C; measurements:12�11·5�4·5 mm (Pl. 1, Figures 1–10)

Description. Orange carnelian (broken in lower leftside). Fortuna, frontal, head facing left. Hair in chignonstyle, calathos and flower on head (partly broken).Dressed in chiton and himation. She is holding acornucopia in her right hand, and her left hand rests ona rudder. The body modelling is schematic and verycoarse and was probably done by a few straight wheeldrill strokes with no detailing. Imperial IncoherentStyle (or Late Groove Style) (Maaskant-Kleibrink,

Roman Wheel-cut Engraving, Dyeing and Painting Microquartz Gemstones 229

1978), or Incoherent Grooves (Henig, 1988). Last halfof 2nd–3rd century . Very common type.

Chemical results. Many barite (BaSO4) grains of1–5 �m in size and many rounded grains of lead (Pb)and tin (Sn) of 1–5 �m in size were detected, as well asa few gold particles and silver sulfide particles of1–100 �m in size found smeared on the head (Pl. 1,Figures 3–5). Their directions do not always coincidewith the engraving direction. The gold particles arecomposed of gold—Au=57%, silver—Ag=23% andcopper—Cu=17%. The blank area of the carnelianstone itself is polished, having many straight thin 1 �mlines of multiple directions (Pl. 1, Figure 7). Themargins bordering the engraving are not sharp andhave a rather weathered look.

No. 2–167—Type F5; measurements:12·8�6·6�2·4 mm (Pl. 2, Figures 1–3)

Description. A narrow oval, thin, translucent yellowbanded agate. Venus-Victrix standing in a 1

4pose,

facing left. Nude but for a small cloth around her hips.She leans backwards with her left elbow resting on acolumn and her left hand behind her body. Right handoutstretched holding a sceptre over her shoulder. Anupright snake in front. Thin ground line. Body model-ling with thick and medium size rounded drills, fewdetailing with short wheel grooves. Imperial ShortGrooves Style (Maaskant-Kleibrink, 1978), or Flavian(Small Grooves Style, Henig 1988). Later 1st–2ndcentury . Basic motif—common; attributes lesscommon.

Chemical results. Many pure gold particles scattered onher body, hair and sceptre having a flaky appearancereaching 10–20 �m in size (Pl. 2, Figures 2–3). The sidemargins of the gemstone have a strong silver line,suggesting silver ring mounting.

No. 3–357—Type F1; measurements: 15�12�2 mm(Pl. 2, Figures 4–7)

Description. An orange translucent carnelian. Apolloleaning to his left, standing on his left foot, facing left.His right hand lowered towards a raven. His left armlowered backwards, bent at the elbow with his lefthand on his waist. In front and to the left a columnwith an unidentified object on top (jar?) and branches.Body modelling with rounded drill. Both legs aresmooth and shining: detailing with a few parallel shortwheel grooves (especially on the bird). Latter ImperialSmall Grooves Style (Maaskant-Kleibrink), orPatterned Style (Henig, 1988). 2nd century . Uncom-mon type for Apollo in a similar pose cf. Maaskant-Kleibrink, 1978, No. 363. For Mercury with a cock cf.Ibid. Nos 668 (sitting), 499, 550, 667, 678 (standingwith lists), and with a column cf. Henig & Whiting(1987, No. 88 from Gadara, Jordan, with lists) andAmorai-Stark (1993, SBF No.64 from Israel).

Chemical results. Within the god’s polished legs area,fine straight scratches of 1–2 �m can be seen (Pl. 2,Figure 6), exhibiting 1–2 �m spherical grains of lead,tin and semi-angular to angular particles of calcium-carbonate (CaCO3) and alumina (Al2O3), as well as fewbarite (BaSO4) grains of 2–10 �m. Iron-oxide remains,surround the carnelian margins, suggesting an iron-ring mounting. (Pl. 2, Figure 7).

No. 4–176—Type F7; measurements:20·3�13·7�4·5 mm (Pl. 3, Figures 1–3)

Description. A white grey fine banded agate. Mercurystanding to the right and facing right, slightly leaningbackwards on his right leg. Nude but with thin draperyover his left shoulder and left arm and a wingeddiadem. Holding a caduceus in his left hand in front ofhis face. His left ankle rests on a decorated motif(column, standard or drapery). He is holding anupright sceptre in his raised right arm with corn andpoppy. Thin short ground line. Body modelling withthick rounded drills; detailing with rounded drills andshort rounded parallel grooves. His eye, lips, chin, noseand neck are clearly delineated. His legs and knees arewell engraved and were probably carefully finished bypolishing. Imperial Short Grooves Style (Maaskant-Kleibrink, 1978), or Flavian Small Grooves Style(Henig, 1988). Latter 1st–early 2nd century . Thesceptre is an unusual feature. For the motif cf.Maaskant-Kleibrink (1978, No. 701).

Chemical results. Abundant grains of 3–5 �m of bariteand limestone (digimap of the spear Pl. 3, Figure 2)as well as lead and iron oxide grains were foundembedded in the engraving area with some scatteredgrains of gold and silver of 1–3 �m in size and copper/zinc (Cu/Zn) 3–5 �m in size.

No. 5–196—Type F5; measurements:15·5�12·3�3 mm (Pl. 3, Figure 4)

Description. Flat oval red carnelian, broken on bothends of longitudinal axial. Cock on Ram, facing left.Large cock standing on a reclining ram’s back. Bodymodelling with large round drill; detailing with manythinner, rounded wheel grooves. The ram’s horns arewell curved forming a half circle of 2 mm diameter.Sassanian-Late Roman work. Later 4th–5th century. Very common motif.

Chemical results. Within the engraving grooves manyremains of barite and limestone grains occur (1–50 �m)with few tin, copper, lead and iron-oxides particles(1–5 �m). Some silver and gold particles 1–10 �m insize were found only within the eye of the ram. Thelimestone found within the grooves here is very hardand was probably used also as white paint, filling theengraved lines.

230 A. Rosenfeld et al.

Roman Wheel-cut Engraving, Dyeing and Painting Microquartz Gemstones 231

No. 6–162—Type C8C; measurements:14·4�11·6�3·8 mm (Pl. 4, Figures 1–5)

Description. White—so-called ‘‘burnt’’ carnelian, orig-inally pale-orange carnelian. Nike-Victory flying to left.Winged. Dressed in chiton with over-fold. In her righthand she is holding a wreath with fillets hanging downand shouldering a palm. Body modelling with roundeddrill, detailing with many parallel rounded wheelgrooves. Imperial Incoherent Style, or Late GrooveStyle (Maaskant-Kleibrink, 1978) or Patterned Style,or Severian Late Patterned Style (Henig, 1988) 2nd–3rd century . Very common motif. For motif andstyle cf. Amorai-Stark (1993, No. SBF 49, with lists,from Israel); Henig & Whiting (1987, Nos 128 motif,133 style, from Gadara, Jordan).

Chemical results. Some alumina (Al2O3) remnants androunded grains of lead, tin and a few copper particlesof 1–10 �m in size, arranged parallel to the groovescould be observed as well as iron oxides particles (Pl. 4,Figure 5). A thin white layer of calcium can be detectedon the surface of the gem as well as within theengraving, where it accumulated in a thicker layer.Within the eye a thick layer of calcium leaving a linearthin brush or wood implement imprint pattern (Pl. 4,Figures 2–4).

No. 7–165—Type C3C; measurements:15·5�11�5·3 mm (Pl. 4, Figure 6)

Description. A three layered agate cabochon of opaquewhite middle layer and honey to brown colour lowerand upper layers. Pantheistic Fortuna-Demeter stand-ing in S shape in 3

4inclination of the body looking to

right. Holding a cornucopia and corn-ear in her righthand and a rudder in her left hand. Behind the goddessa steering oar and a boat. The oar pointing to the right.Body modelling with medium size drills, detailingwith many wheel grooves. Imperial Grooves Style(Maaskant-Kleibrink, 1978), or Flavian (Henig, 1988).Later 1st–2nd century . A very common motif.

Chemical results. Many limestone and barite grainsoccur within the engraving grooves, associated withsome lead and silver grains 1–5 �m in size.

No. 8–304—Type F1 or F5; measurements:14·3�10·5�2·7 mm (Pl. 5, Figures 1–5)

Description. Dark brown black painted carnelian(originally dark orange carnelian; at first glance caneasily be confused with haematite). Two Equestriansconfronted. Left animal—horse or centaur; rightanimal—horse. Both animals raise one fore leg as ifprancing or about to stop. Right rider with calathus onhis head. Both riders with mantels floating behindthem, holding spears ready in upright position. Thespears protrude behind the animals’ heads. Thinground line under both animals. Body modelling withrounded wheel grooves. No scanty detailing. ImperialIncoherent Style (Maaskant-Kleibrink, 1978) or Inco-herent Grooves style (Henig, 1988). Middle 2nd–3rdcentury . For the rare motif and style cf. Amorai-Stark (1993, SBF, No. 105, from Caesarea, Israel).

Chemical results. A thin coherent layer of black paintcomposed of iron-oxide, calcium and phosphorus (P)covers the whole gem surface including the engravings.This brown-black layer can also be seen on the surfaceof the whole gemstone. It was probably smeared by abrush in different directions contrasting the engravingones (Pl. 5, Figure 3). Underneath this layer grains ofbarite, copper, tin and lead (1–10 �m) were found.

b

Plate 1 Figures 1–10. Schematic Fortuna (No. 1-197). Brown carnelian.1. Overview.2. The head.3. Back scattered (B.S.) image of Figure 2. The light grains are AgS. The engraving was painted in silver to emphasize Fortuna’s head.4. Silver sulfide remnants from the paint, of about 100 �m occurred in the head.5. B.S. image of Figure 4.6. A 10 �m gold flake indicating the use of gold for painting the engraved motif.7. A flat surface of the blank area. Straight scratches of 1–2 �m can be observed in many directions, produced by the abrasive material during

the preparatory polishing phase of the gemstone.8. Minute grooves of 10–20 �m probably indicating abrasive grains of similar size that were washed away.9. B.S. image of Figure 8. The light spots are AgS, remains of the silver paint.

10. The spherical grains are lead and tin; the semi-angular grains are barite (BaSO4)—the lubricant used for the engraving-polishing process.The longitudinal grain in the middle is a gold grain.

DiscussionWithin the engraved grooves of the gemstones investi-gated, specific materials were observed with the help ofthe SEM analyzer. Many particles of lead, tin, calcium-carbonate and barite grains of semi-angular to spheri-cal shapes were found together or in variouscombinations almost in all of the engraved studiedgemstones (Table 1). Gold and silver particles werefound in 50% of the gemstones, whereas copper andiron-oxide particles were rare. Most of the lead, tin,copper and barite are small-size grains 1–10 �m. Thissize was probably the smallest grain fraction used bythe Romans for engraving. It is also the smallest size,which still remained about 18 centuries later, due to thecohesion forces. The larger grains were probablywashed away due to owners regular use. The lead, tin,

Plate 2. Figures 1–3. Venus-Victrix with snake (No. 2-167). Banded agate.1. An overview (magnification �8).2. B.S. image of the skirt area. The white 10 �m spots are remains of the gold paint.3. A gold flake.Figures 4–7. Apollo with a raven (No. 3-357). Orange-red carnelian.4. An overview (magnification �8).5. Enlargement of the lower part of the legs of Apollo and the raven (magnification �20).6. Remains of the polishing powder arranged in the lines of the wheel-cut.7. The polishing powder. The spherical grains are lead and tin. The semi-angular grains are alumina, barite and calcium-carbonate.

Roman Wheel-cut Engraving, Dyeing and Painting Microquartz Gemstones 233

Plate 3. Figures 1–3. Mercury (No. 4-176). Banded agate.1. An overview (magnification �8).2. Distribution grain analysis (digimap), showing the polishing powder of BaSO4 and CaCO3 and the lead (Pb) grains (=3–5 �m). Some iron(Fe) grains probably from the drill can be observed.3. The contact between the wheel-cut engraving area and the flat surface area, showing a ‘‘weary’’ effect.Figure 4. Cock on ram (No. 5-196). Carnelian. An overview showing the semi-circular round horns of 2 mm diameter made by a tubular drill(magnification �10).

Plate 4. Figures 1–5. Flying Nike (No. 6-162). Carnelian dyed white.1. An overview—the carnelian gemstone was deliberately painted by CaCO3, heat treated to achieve the white ‘‘burned’’ (‘‘verbrandt’’—inGerman) look of the gemstone produced by a lime coating (magnification �10).2. Nike’s head.3–4. The white calcium paint, smeared by a brush above the eye.5. Digimap analysis, showing within the eye area iron remnants (Fe) from the engraving drill; alumina (Al2O3) from the abrasive powder; lead(Pb) and tin (Sn) from the lubricant agent. (the same scale as in figure 3).Figure 6: Overview of Fortuna (No. 7-165). Banded agate (magnification �8).

Roman Wheel-cut Engraving, Dyeing and Painting Microquartz Gemstones 235

Plate 5. Figures 1–5. Equestrians (No. 8-304). Carnelian.1. Overview (magnification �10).2. B.S. of no. 1 (magnification �10).3. The left animal—detail. The light spots are from the iron oxide paint layer, coated in different directions to the engraving.4. Digimap analysis showing the distribution of elements Fe, P and Ca. The iron oxide is the paint bonded to the orange -brown carnelian by‘‘bone glue’’ (Ca, C and P) achieving the black ‘‘haematite’’ desired colour (the scale here is half of Figure 3).5. The energy dispersive analysis of the surface of the digimap Figure 4, showing the dark paint made of Fe, Ca and P (the silica—Si peak isof the carnelian itself).

236 A. Rosenfeld et al.

Table 1. Summarizing the eight engraved Roman microquartz gemstones: their colour, motifs, and the substancesfound within the grooves

No. Material ColourEngraved

subject ChemistryParticle

sizeParticleshape

1–197 Carnelian Orange Fortuna BaSO4

Sn, PbAg/Au-alloy

1–5 �m1–5 �m1–100 �m

Semi-angularSphericalFlakes

2–167 Banded agate Light/brown translucent Venus Au 10–20 �m Flakes3–357 Carnelian Orange Apollo Pb, Sn

CaCO3, Al2O3

BaSO4

1–2 �m2–10 �m2–10 �m

SphericalSemi-angularSemi-angular

4–176 Banded agate White-grey Mercury CaCO3

BaSO4, PbCu/Zn, Fe2O3

Au, Ag

3–5 �m3–5 �m3–5 �m1–3 �m

Semi-angularSemi-angularSemi-angularFlakes

5–196 Carnelian Red Cock on ram CaCO3, BaSO4

Fe2O3

Pb, Sn, CuAu, Ag

1–50 �m1–5 �m1–5 �m1–10 �m

Semi-angularSemi-angularSphericalLayer

6–162 Carnelian Dyed white; orange orig. Nike CaOAl2O3

Fe2O3

Pb, Sn, Cu

LayerPowder10–40 �m1–10 �m

LayerSemi-angularSemi-angularSpherical

7–165 Banded agate Light honey brown Fortuna-Demeter CaCO3

BaSO4

Pb, Ag

2–10 �m2–10 �m1–5 �m

Semi-angularSemi-angularSemi-spheric.

8–304 Carnelian Paint black; orange orig. Equestrians Fe2O3

Ca, PBaSO4

Cu, Pb, Sn

LayerLayer1–10 �m1–10 �m

LayerLayerSemi-spheric.Spherical

copper, zinc and silver within or on the gemstonesoccur as oxides, but were originally used as metals.Most grounds do not contain high concentrations ofgold, silver, barite, lead, tin and copper, and since allthese particles were well incorporated in the engravingcuts, we excluded these particles as contamination, andconsider them as materials used intentionally duringthe engraving process.

The characteristics of the wheel-cut technology caneasily be observed (e.g. Pl. 1, Figures 1–2). The multi-parallel continuous, longitudinal grooving (even incurve lines), of varying sizes from 50 to 1000 �m resultfrom using different wheel/drill sizes with abrasivepowders of different grain size. Engravings of 0·1, 0·2,0·5, 1, 2 and 3 mm were measured indicating the use ofdrills of these sizes. The iron parallel lines found withinthe grooves of specimen No. 6 (Pl. 4, Figure 5) are anindication of the use of an iron or steel drill/wheel. Theuse of a copper drill could not be ruled out becauserare copper particles were found within the grooves.Only in one sample (No. 4) a brass alloy particle(copper and zinc) was found, that could have origi-nated from a brass drill/wheel, which might have beenused by the Romans. Brass was used regularly by theRomans since the 2nd century (Craddock, 1995,1998).

Gold and silver were found in 50% of the gemstonesin a flaky form rather large in size (100 �m) however,only within the engraving cuts of the motifs. They wereprobably used as paint pigments to emphasis and

decorate the engraved motif. Gold was used by theRomans to enhance and decorate a variety of artisticobjects such as metal and stone statues, vessels, wallpaintings, glass etc. (Porat & Ilani, 1998). A Greco-Roman intaglio is exhibited in the MetropolitanMuseum of Art, New York City (No. L,1992.54.11/a),where the engraving of a chariot with four horses isdecorated in gold. The gold and silver found in ourobjects probably decorated selective parts of the motif(e.g. No. 2–167, Pl. 2, Figures 1–3, within Venus).These finds prove that such motif-painted gemstoneswere not used as seals.

Lead, tin and barite were found in almost all of theinvestigated engraved gems, usually in small sizedgrains of 1–10 �m. Lead and tin were found usually inspherical shape (Pl. 2, Figure 7). They were probablyused as a lubricant paste agent (with oil or water)holding the abrasive powder while cutting. The spheri-cal grains are an indication of high temperature causedby friction during engraving or polishing. Tin, and leadalthough much softer than the gemstones, are used alsotoday for polishing gems. The effect of friction andheat probably helps to achieve a successful polish.Barite is a very heavy mineral and is not known to beused today as an engraving or polishing agent. How-ever, its common occurrence on the gemstones suggeststhat the Romans applied barite for polishing intaglios.Barite frequently occurs in veins and concretionswithin the Turonian–Senonian limestone and chalkbeds in the Levant (e.g. in the Judea Desert). Together

Roman Wheel-cut Engraving, Dyeing and Painting Microquartz Gemstones 237

Table 2. Summary of the chemical materials found within the grooves of the gemstones; their function and applicationin the wheel cut engraving technique

Drill/Wheel MaterialHardness

(Mohs’ scale)

Iron (Fe) 4·0–5·0Steel (Fe+C) 6·0–7·5Bronze (Cu alloyed w. Sn) 5·5–6·0Brass (Cu alloyed w. Zn) 5·0–5·5

Abrasives Alumina (Al2O3) Corundum 9·0Diamond* 10·0

Lubricant Lead (Pb) 1·5Tin (Sn) 1·5–1·8Barite (BaSO4) 3·0–3–5Limestone** 2·0

Artistic media Process Result

Dyeing: white CaCO4—<800�C—CaO Dyeing white gemstonePainting: black Fe2O3+Ca, P, C, Heating(?) Dark magical amuletPainting: gold Gilding by a thin layerPainting: silver Silvering

*After (Scarborough & Nutton, 1986: Pliny, 36,37; Ogden, 1982).**May be contamination from the surrounding ground.

with calcium-carbonate it was mined and grinded, assuch it was probably used as a pigment and/or fillercolourant. Barite was probably also used as alubricant/polishing material by the ancient engraverssimultaneously with the lead, tin and copper. The leadand tin are soft enough to hold the abrasive particles(alumina or diamond). The abrasives were embeddedwithin the lead and tin particles in order to facilitatethe engraving/polishing of hard gemstones. Nowadays,hard gemstone surfaces are polished by alumina ordiamond powder embedded in a tin-lead lap-wheel (H.Stark and Co., expert gem cutters, Ramat-Gan, Israel,personal communication).

Successful experiments of wheel-cut engraving onquartz and microquartz gemstones, were achieved byusing both copper and iron wheels with relative coarsegrit of alumina (emery) as an abrasive of 120–220mesh—grain sizes of approximately 80–160 �m (Sax etal.., 1998). These experiments succeeded in reproduc-ing the same type and pattern of grooves found inancient wheel-cut engraved gemstones.

This shows that, a combination of rotated wheel/drill (steel or bronze) and lubricant (lead, tin andbarite) for holding the abrasives (alumina or diamondpowder) placed within a wet environment such as oil orwater are important for engraving hard gemstones.Since all these materials were found in the samples(except diamond powder), it is evident that the Romanengravers used almost the same technique as today forthe engraving process (Table 2).

Calcium carbonate (chalk, limestone) was probablyused as a white pigment emphasizing the engraving inthe gemstones (e.g. Pl. 3, Figure 4; cf. from Massada;Porat & Ilani, 1998). It seems that just after the

engraving of a carnelian orange gemstone the lime-stone layer in No. 6–162 (Pl. 4, Figures 1–4) was heatedover 800�C to become lime (CaO) which dyed itwhitish. Since hard white gemstones were very muchdesired during the ancient times, but could rarely befound naturally, the engravers aimed at achievingwhite coloured hard gemstones by deliberately ‘‘burn-ing’’ carnelians with calcium carbonate. This could notbe a result of an accidental burning or cremation. Thelack of fracturing in the stone itself (No. 6) and in otherso called ‘‘burned’’ or ‘‘calcified’’ gemstones, indicate acontrolled heating and cooling process which ‘‘dyed’’the gemstone with a uniform white layer. The calcium(lime) penetrated deeply into the stone (about 100–200 �m). The rather thick uniform lime layer as well asthe imprint of the brush found therein (Pl. 4, Figure 2)proves an intentional sophisticated dyeing process. Thegreat porosity of the micro-crystalline quartz due tosize variations in the growth layering of the carnelian,enable an easy whitening/dyeing of gemstone No. 6.This gemstone is especially important since the dyedwhite lime layer, sealed the traces of the material usedin the engraving process. Thus the original particles ofthe iron drill, the lead, tin and barite lubricantmaterial, as well as the alumina abrasive powder,remained confined and could be detected (Pl. 4,Figure 5).

A calcium phosphate ferruginous material (probablywith carbon that could not be detected, because of ourcarbon coating) was found as a thin brown-black equallayer coating the pale orange carnelian gemstone No. 8(Pl. 5, Figures 1–5). Engraving in haematite is veryfrustrating, because it could easily cause an uncon-trolled breakage due to the characteristic crystalline

238 A. Rosenfeld et al.

cleavage. The Romans probably used carnelian, sincethis microquartz has an isotropic physical charactereasy for engraving and then painted it black. Thisiron-oxide mixed with glue (probably bone glue Ca, P,and C, cf. Rosenfeld et al., 2000) exposed to controlledheat treatment, painted the carnelian black-brown col-our. This dark colour imitated haematite and produceda dark gemstone for magical amulets. Charcoal andiron-oxide could have been used also as pigments,emphasizing the engravings motif.

Investigation on engraving techniques and treat-ments of additional microcrystalline quartzes as well ascorundum, glass and garnet gemstones should be fur-ther explored. It would be important also to compareeastern glyptic manufacturing methods to western pro-duction. Research on official seal-stones for theirstamping material could be tantalizing.

Conclusions

(1) Engraving of hard gemstones was done by drill/wheel rotational lathe using abrasive polishingand lubricant materials. The polishing of thesurface of the blank gemstone, was also done by alathe.

(2) Iron, bronze and brass drill/wheels 0·1–3 mm insizes, as well as alumina were found to be used inthe engraving process during the Roman period.The coarse engraving was done by coarse abrasivepowder (50–100 �m in size). Smooth areas werepolished with fine-grained abrasives of 1–10 �m.

(3) The very thin and straight grooves were probablydone with corundum or possibly by a diamondtip.

(4) Small spherical grains of Sn, Pb, as well as barite,participate as lubricants which held the abrasives,facilitating the engraving and polishing process.

(5) Calcium, phosphorus and carbon acted probablyas bone glue, bonding the iron oxides to thegemstone. This mixture was used to paint car-nelian surfaces black.

(6) White hard gemstones were much appreciated bythe Romans (probably due to the symbolic natureof the white colour). Since white hard gemstoneswere rare, the Romans tried to manufacture whitegemstones by deliberately dyeing white the micro-quartz by controlled heat treatment transferringthe calcium-carbonate into lime.

(7) Limestone and barite were probably used also aswhite paint or paste, filling the engraved lines,emphasizing the pictorial pattern for decorationreasons, resulted in attractive jewellery.

(8) Gold (pure or alloyed) and silver were used topaint and decorate engraved motifs in gemstones.This suggests that such gemstones were valuedrather for their decorational than official (i.e.sealstones) value.

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