PETROLOGI

MINERAL TAMBAHAN(Accesory Minerals)Mineral tambahan atau sering disebut juga mineral aksesori ini adalah mineral yang persentasenya sangat sedikit dalam batuan, namun selalu ditemukan. Mineral ini jumlahnya kurang dari 10% dari seluruh komposisi batuan. Dan karena keterdapatannya sangat sedikit, menjadikan mineral-mineral tambahan ini memiliki nilai yang ekonomis yang tinggi. Pada umumnya mineral tambahan ini digunakan untuk perhiasan seperti rutil. Namun ada juga yang digunakan dalam industri dan memiliki nilai yang sangat tinggi seperti zircon. Contoh lainnya dari mineral tambahan ini adalah turmalin.1. Chrysotil KategoriPhyllosilicatesKaolinite-serpentine groupGoreswhite

FormulaMg3(Si2O5)(OH)4Diaphaneitytranslucent

Formula mass277.11 g/molDensity2.53g/ml

Cgrey to GreenRefractive index1.5451.569; 1.5531.571

HabitAcicularBirefringence0.008 (max)

Sistem Kristalmonoclinic or orthorhombicDispersionrelatively weak

PecahanfibrousFusibilitydehydrates at 550750C

Kekerasan23Kilapsilky

2. Magnecite

KategoriCarbonate mineral Kekerasan3.5 - 4.5

FormulaMgCO3KilapVitreous

Formula massGoresWhite

WarnaColorless, white, pale yellow, pale brown, faintly pink, lilac-roseDiaphaneityTransparent to translucent

HabitUsually massive, rarely as rhombohedrons or hexagonal prismsSpecific gravity3.0 - 3.2

Sistem KristalTrigonal - Hexagonal Optical propertiesUniaxial (-)

Belahan[1011] perfectRefractive indexn=1.508 - 1.510 n=1.700

PecahanConchoidalBirefringence0.191

KetahananBrittleFusibilityInfusible

3. Calcite KategoriCarbonate mineralKetahananBrittle

Formula(repeating unit)CaCO3 Kekerasan3 (defining mineral)

Crystal symmetryTrigonal 32/mKilapVitreous to pearly on Belahan surfaces

WarnaColorless or white, also gray, yellow, green,GoresWhite

HabitCrystalline, granular, stalactitic, concretionary, massive, rhombohedral.DiaphaneityTransparent to translucent

Sistem KristalTrigonal hexagonal Specific gravity2.71

KembarCommon by four twin lasOptical propertiesUniaxial (-)

BelahanPerfect on [1011] three directions with angle of 74 55'[1]Refractive indexn = 1.640 1.660 n = 1.486

PecahanConchoidalBirefringence = 0.154 0.174

4. Halloysite KategoriKaolinite-serpentine groupPecahanConchoidal

Formula(repeating unit)Al2Si2O5(OH)4 Kekerasan2 - 2.5

Crystal symmetryMonoclinic domaticKilapPearly, waxy, or dull

WarnaWhite; grey, green, blue, yellow, red from included impurities.DiaphaneitySemitransparent

HabitSpherical cKilaps, massiveSpecific gravity2 - 2.65

Sistem KristalMonoclinicOptical propertiesBiaxial

BelahanProbable on {001}Refractive indexn = 1.553 - 1.565 n = 1.559 - 1.569 n = 1.560 - 1.570

5. Siderite KategoriCarbonate mineralKetahananBrittle

Formula(repeating unit)FeCO3 Kekerasan3.75 - 4.25

WarnaPale yellow to tannish, grey, brown, green, red, black and KilapVitreous, may be silky to pearly

HabitTabular crystals, often curved - botryoidal to massiveGoresWhite

Sistem KristalTrigonal - Hexagonal scalenohedral (3 2/m)DiaphaneityTranslucent to subtranslucent

KembarLamellar uncommon on{0112}Specific gravity3.96

BelahanPerfect on {0111}Optical propertiesUniaxial (-)

PecahanUneven to conchoidalRefractive indexn = 1.875 n = 1.633

DispersionStrongBirefringence = 0.242

6. Dolomite

KategoriCarbonate mineralPecahanConchoidal

Formula(repeating unit)(CaMg)(CO3)2KetahananBrittle

Crystal symmetryTrigonal rhombohedral, 3 Kekerasan3.5 to 4

WarnaWhite, gray to pinkKilapVitreous to pearly

HabitTabular crystalsGoresWhite

Sistem KristalTrigonalSpecific gravity2.842.86

KembarCommon as simple contact twinsOptical propertiesUniaxial (-)

BelahanPerfect on {1011}, rhombohedral BelahanRefractive indexn = 1.6791.681 n = 1.500

7. Chlorite

KategoriPhyllosilicates Kekerasan22.5

Formula(repeating unit)(Mg,Fe)3(Si,Al)4O10(OH)2(Mg,Fe)3(OH)6KilapVitreous, pearly, dull

Warnagreen; rarely yellow, red, or white.GoresPale green to grey

HabitFoliated masses, scaley aggregates, disseminated flakes.Specific gravity2.63.3

Sistem KristalMonoclinic 2/m; Refractive index1.571.67

BelahanPerfect 001PecahanLamellar

8. Kaolin

KategoriKaolinite-serpentine groupKetahananFlexible but inelastic

Formula(repeating unit)Al2Si2O5(OH)4 Kekerasan22.5

WarnaWhite, sometimes red, blue or brown tints from impuritiesKilapPearly to dull earthy

Habitpseudohexagonal plates and cKilaps of plates, aggregated into compact, claylike massesGoresWhite

Sistem KristalTriclinicSpecific gravity2.162.68

BelahanPerfect on {001}

9. Serisit

KategoriGoresPutih

Formula(repeating unit)Ca[Al2Si4O12].2H2O. Kekerasan5.5 6

WarnaTidak berwarna putihKilapKaca

Habitkristal prismatic,surfacerelief sedangGoresWhite

Sistem KristalMonoclinicSpecific gravity2.162.68

PecahanConchoidalDerajat KejernihanTransparan

10. Antigorit Kategori Serpentine mineralPecahan

Formula(repeating unit)(Mg, Fe2 +)3Si2O5(OH)4KetahananBrittle

Crystal symmetryMonoclin Kekerasan2:50-03:00

Warnaputih, coklat, hijau tuaKilapgreasy

HabitGoresputih, putih kehijauan

Sistem KristalMonoclinicSpecific gravity2.61

KembarOptical propertiesBiaxially (-) 61

BelahanmicaceousRefractive index