BAB I

PENDAHULUAN

1.1. LATAR BELAKANG

Dalam study Geologi, setelah mempelajari Kristalografi yang merupakan cabang ilmu

geologi yang paling mendasar, selanjutnya mempelajari cabang ilmu geologi

berikutnya yaitu Mineralogi. Di dalam Mineralogi banyak hal yang harus diketahui

dan dipelajari. Namun dalam tugas ini akan membahas secara rinci tentang mineral

logam, bahwa mineral dikelompokkan menjadi mineral logam dan non logam.

Mineral mempunyai banyak fungsi dan kegunaan dalam kehidupan manusia. Mineral

logam adalah mineral yang mengandung unsur logam atau agregatnya yang dapat

diekstrak dan diolah dengan berbagai rekayasa teknologi menjadi barang yang bernilai

ekonomis dan dipergunakan manusia. Ilmu Mineralogi sangatlah penting untuk

dipelajari sebelum melangkah ke cabang ilmu yang berikutnya yaitu Petrologi.

1.2. MAKSUD DAN TUJUAN

a. Mahasiswa mengetahui mineral dan mineral logam.

b. Mahasiswa mengetahui cara terbentuknya mineral dan tempat didapatkannya di

alam.

c. Mahasiswa mengetahui kegunaan mineral logam.

1.3. RUANG LINGKUP

Makalah ini membahas tentang mineral logam, cara terbentuknya di alam, tempat

didapatkan dan kegunaan logam.

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BAB II

LANDASAN TEORI

1.1. DEFINISI MINERALOGI DAN MINERAL

Mineralogi adalah salah satu cabang ilmu geologi yang mempelajari mengenai mineral, baik

dalam bentuk individu maupun dalam bentuk kesatuan, antara lain mempelajari tentang sifat-

sifat fisik, sifat-sifat kimia, cara terdapatnya, cara terjadinya dan kegunaannya.

Definisi mineral menurut beberapa ahli:

1.    L.G. Berry dan B. Mason, 1959

Mineral adalah suatu benda padat homogen yang terdapat di alam terbentuk secara anorganik,

mempunyai komposisi kimia pada batas-batas tertentu dan mempunyai atom-atom yang

tersusun secara teratur.

2.    D.G.A Whitten dan J.R.V. Brooks, 1972

Mineral adalah suatu bahan padat yang secara struktural homogen mempunyai komposisi

kimia tertentu, dibentuk oleh proses alam yang anorganik.

3.    A.W.R. Potter dan H. Robinson, 1977

Mineral adalah suatu bahan atau zat yang homogen mempunyai komposisi kimia tertentu atau

dalam batas-batas dan mempunyai sifat-sifat tetap, dibentuk di alam dan bukan hasil suatu

kehidupan.

1.2. BATASAN-BATASAN MINERAL

1.2.1. Suatu Bahan Alam

1.2.2. Mempunyai Sifat-Sifat Fisik

1.2.3. Komposisi Kimia Tertentu

1.2.4. Homogen

1.2.5. Anorganik

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1.3. REAKSI BOWEN

BAB III

PEMBAHASAN

1.1. DEFINISI MINERAL LOGAM

Mineral logam adalah  mineral yang mengandung unsur logam atau agregatnya.

1.2. PENGELOMPOKAN MINERAL LOGAM

Mineral  logam dapat dikelompokan dalam 4 (empat) kelompok utama yaitu :

1.1.1. Kelompok Logam Dasar

Logam yang umum terdapat dan secara kimia lebih aktif, misalnya : Tembaga (Cu),

Timbal/Timah Hitam (Pb), Timah (Sn) dan Seng (Zn) dan lain-lain.

Tembaga (Cu)

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PHYSICAL CHARACTERISTICS:

* Color is copper colored with weathered specimens tarnished green.

* Luster is metallic.

* Transparency is opaque.

* Crystal System is isometric; 4/m bar 3 2/m

* Crystal Habits include massive, wires and arborescent or branching forms as the

most common, whole individual crystals are extremely rare but when present are

usually cubes and octahedrons. Occasionally, massive forms will show some

recognizable crystal faces on outer surfaces.

* Cleavage is absent.

* Fracture is jagged.

* Streak is reddish copper color.

* Hardness is 2.5-3

* Specific Gravity is 8.9+ (above average for metallic)

* Associated Minerals are silver, calcite, malachite and other secondary copper

minerals.

* Other Characteristics: ductile, malleable and sectile, meaning it can be pounded

into other shapes, stretched into a wire and cut into slices.

* Notable Occurrences include Michigan and Arizona, USA; Germany; Russia

and Australia.

* Best Field Indicators are color, ductility and crystal habit.

Timbal/Timah Hitam (Pb)

PHYSICAL CHARACTERISTICS:

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* Color is a whitish gray.

* Luster is metallic.

* Transparency is opaque.

* Crystal System is isometric; 4/m bar 3 2/m

* Crystal Habits include small flat platelets and small grains

* Cleavage is absent.

* Fracture is jagged.

* Streak is gray.

* Hardness is 1.5

* Specific Gravity is 11.3+ (very heavy even for metallic minerals)

* Associated Minerals include gold, calcite and hematite.

* Other Characteristics: ductile, malleable and sectile, meaning it can be pounded

into other shapes, stretched into a wire and cut into slices.

* Notable Occurrences includes Franklin, New jersey, USA; Harstig Mine,

Sweden; Vera Cruz, Mexico and in placer mines especially in the Ural Mountains

of Russia.

* Best Field Indicators are color, density, hardness, luster and ductility.

Timah (Sn)

PHYSICAL CHARACTERISTICS:

* Color is white to gray.

* Luster is metallic.

* Transparency: Specimens are opaque.

* Crystal System is tetragonal (below 13.2 degrees C tin converts to isometric).

* Crystal Habits include grains in placer deposits and lab grown specimens.

* Cleavage is indistinct.

* Hardness is 1.5 - 2.

* Specific Gravity is 7.3 (heavy even for a metallic mineral).

* Streak: white - gray.

* Other Characteristics: Sectile.

* Associated Minerals include native gold, native copper, stistaite, native

aluminum and other rare native metals.

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* Notable Occurrences include the type locality of Aberfoil and Sam Rivers,

Oban, New South Wales and Tasmania, Australia; Miass River, Southern Urals;

Amur, Yakutia; Tolbachik, Kamchatka Peninsula and Aldan Shield, Siberia,

Russia.

* Best Field Indicators are color, brittleness, hardness, locality and density.

Seng (Zn)

PHYSICAL CHARACTERISTICS:

* Color is white to bright blue gray.

* Luster is metallic.

* Transparency: Specimens are opaque.

* Crystal System is hexagonal; 6/m 2/m 2/m.

* Crystal Habits include volcanic exhalations, granular (often microscopic) and

lab grown specimens.

* Cleavage is perfect in one direction (basal).

* Hardness is 2.

* Specific Gravity is 6.9 - 7.2 (heavy even for a metallic mineral).

* Streak: Light gray.

* Other Characteristics: Brittle at room temperatures (not malleable or ductile

unless heated to 100 degrees C).

* Associated Minerals include native gold, native copper, native aluminum and

other rare native metals.

* Notable Occurrences include the type locality of Mina Dulcinea de Llampos,

Copiapo, Chile and Elsa Mine, Keno Hill-Galena Hill area of the Yukon

Territory, Canada as well as New Brunswick, Victoria and Forest Range Gold

Mine, Australia; Tyrol, Austria; Amur, Yakutia; Chirynaisky Massif, Koryak

Mts., Kamchatka Peninsula and Billeekh Intrusion, Siberia, Russia.

* Best Field Indicators are color, brittleness, hardness, locality and density.

1.1.2. Kelompok Logam Mulia

Logam yang secara ekonomis sangat berharga dan banyak dibutuhkan, terdiri dari :

emas (Au), Perak (Ag) dan Platina (Pt). Dalam kedua kelompok ini satu sama lain

selalu berkaitan, bisa dalam bentuk urat maupun dalam bentuk sebaran dalam batuan,

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khusus untuk emas selain terkemas dalam bentuk urat, biasanya dalam urat kuarsa,

juga bisa terdapat sebagai emas alluvial yang tersebar di bekas undak-undak sungai

tua atau tersebar di endapan pasir sungai yang masih aktif. Logam Dasar dan Logam

Mulia yang terbentuk dalam urat biasanya di Indonesia khususnya terjadi dalam

lingkungan batuan gunungapi dan populer disebut Emas Epitermal. Sudah barang

tentu disebut demikian setelah memenuhi kriteria-kriteria pembentukkannya.

Emas (Au)

PHYSICAL CHARACTERISTICS:

* Color is golden "butter" yellow.

* Luster is metallic.

* Transparency is opaque.

* Crystal System is isometric; 4/m bar 3 2/m

* Crystal Habits include massive nuggets and disseminated grains. Also wires,

dendritic and arborescent crystal clusters.

* Cleavage is absent.

* Fracture is jagged.

* Streak is golden yellow.

* Hardness is 2.5 - 3

* Specific Gravity is 19.3+ (extremely heavy even for metallic minerals)

* Associated Minerals include quartz, nagyagite, calaverite, sylvanite, krennerite,

pyrite and other sulfides.

* Other Characteristics: ductile, malleable and sectile, meaning it can be pounded

into other shapes, stretched into a wire and cut into slices.

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* Notable Occurrences include California and South Dakota, USA; Siberia,

Russia; South Africa; Canada and other localities around the world.

* Best Field Indicators are color, density, hardness, sectility, malleability and

ductility.

Perak (Ag)

PHYSICAL CHARACTERISTICS:

* Color is lead gray to black.

* Luster is metallic.

* Transparency: Crystals are opaque.

* Crystal System: Monoclinic; 2/m below 173 degrees Celsius (acanthite) and

isometric; 4/m bar 3 2/m above (argentite).

* Crystal Habits include rarely well formed pseudo: cubes, octahedrons and

dodecahedrons. Non-argentite crystals (those that formed below 173 degrees

Celsius) of acanthite tend to be of a slender prismatic habit. More commonly

found massive and as coatings or as arborescent (branching) and reticulated

groups.

* Cleavage is absent.

* Fracture is conchoidal.

* Hardness is 2.5 - 3

* Specific Gravity is approximately 5.5 - 5.8 (slightly heavy even for metallic

minerals).

* Streak is a shiny black.

* Other Characteristics: Sectile, meaning it can be cut with a knife like lead and

fresh shiny surfaces will eventually form a dull coating after prolonged exposure

to light (can be removed by ultrasonic treatment).

* Associated Minerals include silver, quartz, bornite, gold, galena, proustite,

pyrargyrite, stephanite and other silver sulfide minerals.

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* Notable Occurrences include Guanajuato, Mexico; Freiberg and Saxony,

Germany; Cobalt, Ontario, Canada; Comstock Lode, Nevada and Butte, Montana,

USA; Cornwall, England; Chile; Peru; Bolivia and especially Kongsberg,

Norway.

* Best Field Indicators are crystal habit, density, softness, sectility, association

with other silver sulfosalts and color.

Platina (Pt)

PHYSICAL CHARACTERISTICS:

* Color is a white-gray to silver-gray, usually lighter than the platinum color of

pure processed platinum.

* Luster is metallic.

* Transparency is opaque.

* Crystal System: Isometric; 4/m bar 3 2/m

* Crystal Habits include nuggets, grains or flakes, rarely showing cubic forms.

* Cleavage is absent.

* Fracture is jagged.

* Hardness is 4 - 4.5

* Specific Gravity is 14 - 19+, pure platinum is 21.5 (extremely heavy even for

metallic minerals).

* Streak is steel-gray.

* Other Characteristics: Does not tarnish, is sometimes weakly magnetic and is

ductile, malleable and sectile, meaning it can be pounded into other shapes,

stretched into a wire and cut into slices.

* Associated Minerals include chromite, olivine, enstatite, pyroxene, magnetite

and occasionally gold.

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* Notable Occurrences includes Transvaal, South Africa; Ural Mountains, Russia;

Columbia and Alaska, USA.

* Best Field Indicators are color, density, weak magnetism, hardness, associations

and ductility.

1.1.3. Kelompok Logam Jarang

Logam yang secara relatif, ditemukan dalam jumlah sedikit dan tersebar di bumi.

Unsur-unsur logam ini, jarang ditemukan terkonsentrasi dalam jumlah banyak.

Beberapa diantaranya adalah : Lithium (Li), Yurium (Y), Zirconium (Zr), Logam

Tanah Jarang (Rare Earth Elements; unsur yang mempunyai Nomor Atom 57 s.d. 71),

Indium (In), Cadmium (Cd) dan lain-lain.

Lithium (Li)

Yurium (Y)

Zirconium (Zr)

PHYSICAL CHARACTERISTICS:

* Color is brown, red, yellow, green, blue, black, and colorless.

* Luster is adamantine.

* Transparency crystals are transparent to translucent.

* Crystal System tetragonal; 4/m 2/m 2/m

* Crystal Habits: dipyramidal and prismatic as discussed above.

* Cleavage indistinct in two directions, prismatic.

* Fracture is uneven

* Hardness is 7.5

* Specific Gravity is 4.6-4.7

* Streak white

* Associated Minerals albite, biotite, garnets, xenotime and monazite.

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* Other Characteristics: is sometimes fluorescent and darker crystals may be

radioactive due to impurities of rare earth elements. Also index of refraction is

1.92 - 2.01

* Notable Occurances Seiland, Norway; Pakistan; Russia; Bancroft and Sudbury,

Ontario, Canada and New Jersey and Colorado, USA.

* Best Field Indicators are crystal habit, hardness, luster and density.

Indium (In)

Cadmium (Cd)

Kegunaan  unsur-unsur logam jarang umumnya untuk teknologi tinggi seperti : barang

elektronik, katalis dalam pengolahan minyak bumi, keramik tahan panas dan lain-lain.

1.1.4. Kelompok Mineral Logam Besi dan Campuran Besi

Logam yang lazim digunakan dalam industri besi dan campurannya, seperti : Besi

(Fe), Kobal (Co), Kromit (Cr), Mangan (Mn) dan  lain-lain.

Besi (Fe)

PHYSICAL CHARACTERISTICS:

* Coloris steel gray or black.

* Luster is metallic.

* Transparency is opaque.

* Crystal System is isometric; 4/m bar 3 2/m

* Crystal Habits crystal form is extremely rare, when etched, meteoritic examples

may show interesting and complicated intergrowths of cystals according to

different nickel-iron concentrates. Terrestrial samples are massive and appear as

small flakes and irregular masses. Meteoritic samples are usually rounded, pitted

and irregular.

* Cleavage is absent but crystals will have distinct parallel partings.

* Fracture is hackly.

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* Streak is gray metallic.

* Hardness is 4-5

* Specific Gravity is 7.3-7.8 (heavy even for metallic)

* Other Characteristics: malleable, strongly attracted to magnets.

* Associated Minerals are olivine, pyroxenes, and some minerals that are only

found in meteorites. In terrestrial samples it is found with gold and platinum and

with sulfide ores.

* Notable Occurrences for meteoritic iron are best found in Antarctica, where

meteorites are easy to spot against a background of snow and ice. Many

specimens are found in Diablo Canyon, Arizona, USA; and in Gibbeon, Hoba,

Namibia. Also Meteor Crater (Barringer Crater), Arizona, USA; Australia;

Poland and elsewhere. For terrestrial iron, good specimens can be found in the

Kola Pennisula, Russia; Disco Island, Greenland; Kassel, Germany and New

Zealand.

* Best Field Indicators are color, malleability, attraction to magnets and forms.

Kobal (Co)

PHYSICAL CHARACTERISTICS:

* Color is steel grey.

* Luster is metallic.

* Transparency: Specimens are opaque.

* Crystal System is isometric.

* Crystal Habits include only lab grown specimens.

* Specific Gravity is 8.9 (very heavy for a metallic mineral).

* Other Charateristics: Magnetic.

* Notable Occurrences include only lab grown specimens.

* Best Field Indicators are color, magnetism and density.

Kromit (Cr)

PHYSICAL CHARACTERISTICS:

* Color is white.

* Luster is metallic.

* Transparency: Specimens are opaque.

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* Crystal System is isometric; 4/m bar 3 2/m.

* Crystal Habits are limited to granular specks and labratory grown specimens.

* Hardness is 4

* Specific Gravity is 7.21 (heavy for a metallic mineral).

* Associated Minerals include diamond, spinel, copper and iron.

* Notable Occurrences include the type locality in Sichuan, China as well as the

Udachnaya (Lucky) pipe, Yakutia, Russia.

* Best Field Indicators are color, locality, hardness and density.

Mangan (Mn)

PHYSICAL CHARACTERISTICS:

* Color is steel or silver grey.

* Luster is metallic.

* Transparency: Specimens are opaque.

* Crystal System is isometric.

* Crystal Habits include only lab grown specimens.

* Specific Gravity is 7.44 (very heavy for a metallic mineral).

* Notable Occurrences include only lab grown specimens.

* Best Field Indicators are color and density.

BAB IV

PENUTUP

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1.1. KESIMPULAN

DAFTAR PUSTAKA

http://geologiblankfive.wordpress.com/2011/06/25/mineral-logam/

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