Komposisi Mineral Pada Batuan
Sifat fisis batuan adalah konsekuensi dari komposisi mineralnya. Mineral di sini didefinisikan sebagai elemen kimia atau senyawa yang terbentuk secara alami sebagai hasil dari proses inorganik. Analisis kimia dari enam batuan pasir dengan emisi spektrografi dan pemindaian dispersi sinar-X pada mikroskop electron menunjukkan bahwa batuan hanya terdiri dari beberapa elemen kimia . Analisis batuan menggunakan spektroskopi emisi menghasilkan komposisi kimia matriks dengan mencampur batuan dan lithium untuk membuat semua elemen larut dalam air kemudian menganalisis total emisi spektograf.
Pemindaian mikroskop elektron sinar-X hanya dapat menganalisis bitnik-bintik mikrokopik pada permukaan batuan yang pecah. Perbedaan antara analisis kimia dari sampel total dan analisis bintik-bintik permukaan sangat signifikan untuk pertimbangan interaksi fluida dan batuan.
Keberadaan logam transisi pada permukaan batuan menginduksi preferensi pembasahan di permukaan oleh minyak, melalui reaksi tipe asam-basa Lewis antara senyawa organik polar dalam minyak mentah dan logam transisi yang terekspos pada pori. Konsentrasi alumunium yang tinggi di permukaan dicantumkan dalam tabel di bawah yang mungkin tergantung pada keberadaan mineral lempung yang banyak terkandung dalam batupasir. Tabel ini merupakan hasil analisis dari enam batupasir.
Meskipun kerak tampak sangat heterogen sehubungan dengan mineral dan jenis batuan, sebagian besar mineral pembentuk batuan terdiri dari silikon dan oksigen bersama dengan aluminium dan satu atau lebih elemen lain yang tercantum dalam tabel berikut.
Komposisi kimia dan deskripsi kuantitatif dari beberapa mineral tercantum dalam tabel berikut.
Beberapa mineral sangat rumit dan formula kimianya berbeda dalam berbagai publikasi; dalam kasus seperti itu, formula paling umum yang dilaporkan dalam daftar referensi dipilih.
Nama Mineral | Deskripsi |
---|---|
Agate (Chalcedony) - SiO2 | silicon dioxide; waxy luster; H (hardness) = 7 |
Anhydrite-CaSO4 | calcium sulfate; white-gray; H = 2 |
Apatite-Ca5(PO4)3F | fluorapatite; H = 4 |
Asbestos (Serpentine) -Mg6Si4O10(OH)8 | hydrous magnesium silicate; light green to dark gray; greasy or waxy; H = 3 |
Augite (Pyroxene group) -(Ca, Na)(Al, Fe 2+, Fe3+, Mg)(Si,Al)2O6 | Alkali, ferromagnesium, alumunium silicates; dark green to black; exhibits cleavage; large, complex group of minerals; H = 5 |
Barite-BaSO4 | barium sulfate; white, light blue, yellow, or red; pearly luster, H = 3 |
Beryl-Be3d2Si6O18 | clear beryl forms the blue-green aquamarine and green emerald gems; exhibits cleavage. Beryl is an ore of the element beryllium; H = 7-8 |
Biotite (Mica) -K(Fe, Mg)3(AlSi3O10)(OH)2 | hydrous potassium, ferro- magnesium, aluminum silicate; dark green to black (black mica); vitreous; exhibits cleavage; rock-forming mineral; H = 3 |
Calcite-CaCO3 | calcium carbonate; colorless or white to light brown, vitreous; effervesces in dilute HC1; H = 3 |
Celestite-SrSO4 | strontium sulfate; colorless; H = 3. Chalk-CaC03 : calcite; white; soft fine-grained limestone formed from microscopic shells; effervesces with dilute HCl; H = 2-3 |
Chlorite-(Al, Fe, Mg)6(Al, Si)4010(OH)8 | hydrous ferro-magnesium, aluminum silicate; shades of green (green mica); exhibits cleavage; rock-forming mineral; H = 3 |
Cinnabar-HgS | mercury sulfide; red to brownish-red; luster is dull. Only important ore of mercury; H = 2.5 |
Cordierite-Al4(Fe, Mg)2Si5018 | ferro-magnesium aluminum silicate; blue; vitreous; H = 7 |
Corundum-Al2O3 | red varieties are rubies and other colors are known as sapphire; H = 9 |
Diatomite-SiO2 | silica; white; formed from microscopic shells composed of silica; distinguished from chalk by lack of effervescence with dilute HCl; H = 1-2 |
Dolomite-CaMg(CO3)2 | calcium-magnesium carbonate; pink or light brown, vitreous-pearly; effervesces in HCl if powdered; H = 3 |
Feldspar (Orthoclase, Potassium feldspar)-KalSi3O8 | white to pink; vitreous; large crystals with irregular veins; exhibits cleavage; rock-forming mineral; H = 6 |
Feldspar (Plagioclase)-CaAl2Si208 and NaAlSi3O8(Albite) | calcium and sodium aluminum silicate; white to green; vitreous; exhibits cleavage; rock-forming mineral; H = 6 |
Fluorite-CaF2 | calcium fluorite; H = 4. Galena-PbS: lead sulfide; lead-gray; bright metallic luster; lead ore; H = 2.5 |
Graphite-C | carbon; gray to black; metallic luster; H = 2 |
Gypsum-Cas04 .2H20 | hydrous calcium sulfate; transparent to white or gray; vitreous-pearly-silky; H = 2 |
Halite-NaCl | sodium chloride; colorless to white; vitreous-pearly; H = 2 |
Hematite-Fe2O3 | iron oxide (the most important iron ore); reddish-brown to black or gray, H = 6 |
Hornblende (Amphibole group)-Ca2Na(Fe2, Mg)4(Al, Fe3, Ti)(Al, Si)8(O, OH)2 | hydrous alkali, ferro-magnesium, aluminum silicates; dark green to black; exhibits cleavage. The iron and magnesium impart the dark color. H = 5 |
Illite (Muscovite)-KAl2(AlSi3O10)(OH)2 | hydrous potassium-aluminum silicate; clear to light green, vitreous; not chemically well-defined but with the approximate composition of muscovite; H = 2.5 |
Kaolinite (Clay)-Al4(Si4010)(OH)4 | hydrous aluminum silicate; light colored;H = 1-2 |
Limonite (Goethite)-FeO(OH). H2O | hydrous iron oxide; yellow-brown to dark brown; H = 5 |
Magnetite-Fe3O4 | iron oxide; black metallic luster; strongly magnetic iron ore; H = 6 |
Montmorillonite (Smectite clay)-(CaNa)(Al, Fe, Mg)4 (Si, Al)8(OH)8 | generally light colored; H = 1 |
Muscovite (Mica)-KAl2(AlSi3O10)(OH)2 | hydrous potassium-aluminum silicate; clear to light green; vitreous; rock-forming mineral; H = 2.5 |
Olivine-Fe, Mg)2Si04 | ferro-magnesium silicate; clear to light green, various shades of green to yellow; vitreous (glassy) luster with crystals in the rock; H = 7 |
Opal-Si02 . nH20 | hydrous silicon dioxide; variety of almost any color; glassy luster; H = 5 |
Pyrite-FeS2 | iron sulfide; pale yellow; bright metallic luster; H = 6 |
Quartz-SiO2 | silicon dioxide; clear (transparent) or with a variety of colors imparted by impurities (purple amethyst, yellow citrine, pink rose quartz, brown smoky quartz, snow white chert, multiple colored agate); glassy luster; H = 7 |
Serpentine–MgSi2O5(OH)4 | hydrous magnesium silicate; beige color; H = 3 |
Siderite-FeCO3 | ferrous carbonate; light colored to brown; H = 3-4 |
Sphalerite-ZnS | zinc sulfide; yellow to dark brown or black; resinous luster; exhibits cleavage; zinc ore; H = 3 |
Sulfur-S | yellow; resinous; H = 1-2 |
Sylvite-KCl | potassium chloride; colorless to white; H = 1-2. |
Talc-Mg3(Si4O10)(OH)2 | hydrous magnesium silicate; green, gray, or white; soapy to touch; H = 1 |
Topaz-Al2(SiO4)(Fe,OH)2 | yellow, pink, blue-green; exhibits cleavage; H = 8 |
Turquoise-CuAl6(PO4)4(OH)8.2H20 | blue or green color; H = 5 |
Vermiculite-Mg3Si4O10(OH)2nH2O | hydrous magnesium silicate; light colored; H = 1 |
Bagaimana kandungan mineral pada batuan beku, sedimen dan metamorf?