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2. Lustre (mineralogy) - Wikipedia

   en.wikipedia.org/wiki/Lustre_(mineralogy)

   Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux, meaning "light", and generally implies radiance, gloss, or brilliance. A range of terms are used to describe lustre, such as earthy ...

3. Quartz - Wikipedia

   en.wikipedia.org/wiki/Quartz

   Quartz. Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO 4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO 2. Quartz is, therefore, classified structurally as a framework silicate mineral ...

4. Smoky quartz - Wikipedia

   en.wikipedia.org/wiki/Smoky_quartz

   Smoky quartz. Smoky quartz is a brownish grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystals. [6] The color of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates color centers around aluminum impurities within ...

5. Adularescence - Wikipedia

   en.wikipedia.org/wiki/Adularescence

   Adularescence. Adularescence in a moonstone cabochon, Minas Gerais, Brazil. The specimen's diameter is 23 mm (0.91 in). Adularescence (/ ˌædʒələˈrɛsəns / AJ-ə-lə-RES-əns) is an optical phenomenon that is produced in gemstones like moonstone. The optical effect is similar to labradorescence and aventurescence.

6. 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 ...

7. Tiger's eye - Wikipedia

   en.wikipedia.org/wiki/Tiger's_eye

   Luster. Silky. Specific gravity. 2.64–2.71. Tiger's eye (also called tiger eye) is a chatoyant gemstone that is usually a metamorphic rock with a golden to red-brown colour and a silky lustre. As members of the quartz group, tiger's eye and the related blue-coloured mineral hawk's eye gain their silky, lustrous appearance from the parallel ...

8. Jasper - Wikipedia

   en.wikipedia.org/wiki/Jasper

   Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, [1][2] is an opaque, [3] impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron (III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as ...

9. Porphyry (geology) - Wikipedia

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

   Porphyry (geology) Porphyry (/ ˈpɔːrfəri / POR-fə-ree) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate -rich, generally aphanitic matrix or groundmass. In its non-geologic, traditional use, the term porphyry usually refers to the purple-red form of ...