Rock-forming minerals are the essential minerals that make up most of Earth’s rocks. These minerals are found in igneous, sedimentary, and metamorphic rocks and are mainly composed of elements like silicon (Si), oxygen (O), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg).
Table of Rock forming Minerals
| Sl No | Name Of Mineral | Composition | Hardness | Colour | Lustre | Cleavage, Fracture | Form, Distinctive Feature |
|---|---|---|---|---|---|---|---|
| 1 | Actinolite | Hydrous silicate of Ca, Mg, Fe | 5-6 | Green | Vitreous | 2 Perfect At 56° And 124° | Fibrous (Asbestos), Long Prismatic Crystals, Radiating Aggregates |
| 2 | Agate | Microcrystalline silica | 6.5 | Different Coloured Band | Vitreous | Conchoidal Fracture | Banded Structure |
| 3 | Andalusite | Al₂SiO₅ | 7.5 | Grey, Pink, Red | Vitreous | Poor | Columnar Crystals, Granular |
| 4 | Apatite | Ca₅F(PO₄)₃ | 5 | Greenish, Bluish, Reddish, Yellow | Vitreous | Poor | Hexagonal Crystals, Massive |
| 5 | Asbestos | Mg₆Si₄O₁₀(OH)₈ | 2 | Yellow | Silky | Perfect | Fibrous |
| 6 | Augite | Ca, Mg, Fe, Al, silicate | 5-6 | Black, Dark Green | Vitreous | 2 Good At 90° | Short Prismatic Crystals, Square, Rectangular or Octagonal Prisms |
| 7 | Beryl | Be₃Al₂(SiO₃)₆ | 7.5-8 | White, Yellow, Greenish or Bluish Green | Vitreous | Poor | Hexagonal Crystals, Massive |
| 8 | Biotite | Silicate of K, Mg, Fe, Al with H₂O | 2.5-3 | Black, Dark Brown | Submetallic Peary | Perfect Basal | Foliated Masses, Scaly Aggregates. Thin Elastic Laminae |
| 9 | Calcite | CaCO₃ | 3 | Colourless Or White, Also with Grey, Yellow or Red Tints | Vitreous | 3 Perfect at Oblique Angles, Yields Rhombohedral Pieces | Coarsely To Finely Crystalline, Good Crystals Common. Vigorous Bubbling Beneath a Drop of Dilute HCL |
| 10 | Chalcedony | Microcrystalline SiO₂ | 6.5 | White, Frey, Blue, Brown, Black | Waxy, Greasy | Conchoidal Fracture | Botryoidal, Stalactitic. Occurs In Veins or Banded Aggregate |
| 11 | Chert | Microcrystalline SiO₂ | 6.5 | Black, Grey | Greasy | - | Bands, Irregular Nodules |
| 12 | Chlorite | Complex silicate of Fe, Mg, Al with H₂O | 2-2.5 | Green, Black | Resinous, Pearly | Perfect | Foliated Masses, Scales, Drains, Greasy Feel |
| 13 | Corundum | Al₂O₃ | 9 | Brown, Pink, Blue, Gem Varieties: Ruby. Sapphire | Vitreous | Uneven Fracture | Rounded, Barrel Shaped Crystals, Often As Granular Masses (emry) |
| 14 | Dolomite | CaMg(CO₃)₂ | 3.5-4 | Colourless, White, Variously Coloured by Impurities | Vitreous, Dull | 3 Perfect | Rhombohedral Crystals, Granular, Massive, Less Vigorous effer-Vescence in Cold HCL |
| 15 | Flint | Microcrystalline SiO₂ | 7 | Black Shades of Grey | Greasy, Waxy | - | Bands, Irregular Nodules |
| 16 | Fluorite | CaF₂ | 4 | Colourless, Purple, Violet, Blue, Green, Yellow | Vitreous | Perfect Octahedral | Octahedrons, Cubes, Also Granular |
| 17 | Garnet | Ca, Mg, Fe, Al silicate | 7.5 | Red, Brown | Resinous, Vitreous | Conchoidal Fracture | Isometric Crystal or Rounded, Specific Gravity 3.6-4.3 |
| 18 | Gypsum | CaSO₄·2H₂O | 2 | Colourless, White, Also Grey, Yellowish or Red | Pearly Silky | Perfect | Granular, Earthy, Tabular Crystals, Fibrous |
| 19 | Hornblende | Complex silicate of Ca, Na, Mg, Fe, Al with (OH) ions | 5-6 | Black, Greenish Black | Vitreous | 2 Good At 56° And 124° | Long Crystals Usually 6- Sided. Also, In Granular Masses |
| 20 | Jasper | Microcrystalline SiO₂ | 7 | Red, Yellow, Brown, Green | Greasy | - | Massive |
| 21 | Kaolinite | Hydrous silicate of Al | 1-2 | White, Grey, Yellowish | Earthy, Dull | Uneven Fracture | Massive, Greasy Feel and Argillaceous Smell |
| 22 | Kyanite | Al₂SiO₅ | 5 Length Wise & 7 Across Crystals | White, Pale, Blue, Grey, Green | Vitreous, Pearly | 1 Perfect | Long Bladed Habit |
| 23 | Microcline | KAlSi₃O₈ | 6 | Green, Bluish Green, Pink, Grey | Pearly, Vitreous | 2 At Right Angles | Massive, Prismatic Crystals, Striations on Basal Pinacoid Due to Twinning |
| 24 | Muscovite | Hydrous silicate of Al and K | 2-3 | Transparent White | Pearly | Perfect Basal | Foliated, Thin Flexible Elastic Laminae |
| 25 | Opal | Amorphous silica SiO₂·nH₂O | 5.5-6.5 | White, Grey, Yellow, Red | Greasy | Massive, Shows Play of Colour | |
| 26 | Orthoclase | KAlSi₃O₈ | 6 | White, Red Grey | Vitreous Pearly | 2 Perfect at Right Angles | Prismatic Crystals, Tabular, Massive |
| 27 | Olivine | (Mg,Fe)₂SiO₄ | 6.5-7 | Olive-Green, Brown | Vitreous | Conchoidal Fracture | Granular Mass |
| 28 | Plagioclase | (Soda-lime feldspars) Na, Ca, Al silicate | 6 | White To Grey | Vitreous | 2 Perfect at Right Angles | Tabular, Fine Parallel Striations on Perfect Cleavage |
| 29 | Quartz | SiO₂ | 7 | Purple (Amethyst), Dark-Grey (Smokey Quartz), Colourless (Rock Crystal), Pink (Rose Quartz) | Vitreous | Conchoidal Fracture | 6 Sided Prismatic Crystals, Also Granular and Massive |
| 30 | Serpentine | Mg₆Si₄O₁₀(OH)₈ | 4-6 | Green, Yellow, Brown | Waxy, Greasy, Silky | Splintery Frature | Fibrous Or Platy Masses |
| 31 | Silimanite | Al₂SiO₅ | 6-7 | Grey, White, Brown | Resinous | Poor | Long Needle-Shaped Crystals, Felted Masses |
| 32 | Staurolite | Hydrous silicate of Al and Fe | 7 | Brwon, Brwonish Black, Yellow | Resinous | Poor | Short Prismatic Crystals, Some Cross Shaped |
| 33 | Talc | Mg₃Si₄O₁₀(OH)₂ | 1 | White, Pale-Green | Pearly, Greasy | 1 Perfect | Foliated, Massive, Soapy Feel |
| 34 | Topaz | (AlF)₂SiO₄ | 8 | Colourless, Yellow, Bluish, Greenish | Vitreous | 1 Good | Prismatic Crystals, Granular, Massive |
| 35 | Tourmaline | Complex boro-silicate of Al, with Na, Fe, Mg, Ca and K | 7.5 | Black, Blue, Green | Vitreous | - | Crystal, Hexagonal, Or Triangular in Cross-section |
| 36 | Tremolite | Hydrous silicate of Ca, Mg | 5-6 | White, Grey | Vitreous | 2 Perfect | Radiating Fibrous Crystals |