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  2. Quartz - Wikipedia

    en.wikipedia.org/wiki/Quartz

    Quartz is the mineral defining the value of 7 on the Mohs scale of hardness, ... Pure quartz, traditionally called rock crystal or clear quartz, ...

  3. Quartzite - Wikipedia

    en.wikipedia.org/wiki/Quartzite

    Quartzite is a very hard rock composed predominantly of an interlocking mosaic of quartz crystals. The grainy, sandpaper-like surface is glassy in appearance. Minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization, causing streaks and lenses to form within the quartzite. [ 1 ]

  4. Mohs scale - Wikipedia

    en.wikipedia.org/wiki/Mohs_scale

    Hardness may be difficult to determine, or may be misleading or meaningless, if a material is a mixture of two or more substances; for example, some sources have assigned a Mohs hardness of 6 or 7 to granite but it is a rock made of several minerals, each with its own Mohs hardness (e.g. topaz-rich granite contains: topaz — Mohs 8, quartz ...

  5. Quartz-porphyry - Wikipedia

    en.wikipedia.org/wiki/Quartz-porphyry

    Phenocrysts of clear glassy rounded quartz and white orthoclase feldspar are set in a fine-grained matrix. Sample is just over 10 cm long. Quartz-porphyry, in layman's terms, is a type of volcanic rock containing large porphyritic crystals of quartz. [1] [2] These rocks are classified as hemi-crystalline acid rocks.

  6. List of gemstones by species - Wikipedia

    en.wikipedia.org/wiki/List_of_gemstones_by_species

    Rose quartz (var.) Rock crystal (var.) Shocked quartz (var.) Smoky quartz (var ... Metal-coated crystals hyped as rainbow quartz; Lab spinel; Synthetic turquoise ...

  7. Conglomerate (geology) - Wikipedia

    en.wikipedia.org/wiki/Conglomerate_(geology)

    Conglomerate (/ k ən ˈ ɡ l ɒ m ər ɪ t /) is a sedimentary rock made up of rounded gravel-sized pieces of rock surrounded by finer-grained sediments (such as sand, silt, or clay). The larger fragments within conglomerate are called clasts, while the finer sediment surrounding the clasts is called the matrix.

  8. Chert - Wikipedia

    en.wikipedia.org/wiki/Chert

    Chert (/ tʃ ɜːr t /) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, [1] the mineral form of silicon dioxide (SiO 2). [2] Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.

  9. Granodiorite - Wikipedia

    en.wikipedia.org/wiki/Granodiorite

    According to the QAPF diagram, granodiorite has a greater than 20% quartz by volume, and between 65% and 90% of the feldspar is plagioclase. A greater amount of plagioclase would designate the rock as tonalite. Granodiorite is felsic to intermediate in composition. It is the intrusive igneous equivalent of the extrusive igneous dacite.