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2. Agate - Wikipedia

   en.wikipedia.org/wiki/Agate

   Agate (/ ˈ æ ɡ ɪ t / AG-it) is a variety of chalcedony, [1] which comes in a wide variety of colors. Agates are primarily formed within volcanic and metamorphic rocks.The ornamental use of agate was common in Ancient Greece, in assorted jewelry and in the seal stones of Greek warriors, [2] while bead necklaces with pierced and polished agate date back to the 3rd millennium BCE in the Indus ...

3. Pegmatite - Wikipedia

   en.wikipedia.org/wiki/Pegmatite

   Pegmatite. A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite.

4. List of U.S. state minerals, rocks, stones and gemstones

   en.wikipedia.org/wiki/List_of_U.S._state...

   Rose quartz (1966) Fairburn agate (1966) and State Jewelry: Black Hills Gold: Tennessee [66] Agate (2009) Limestone (from 1979 to present) and formerly.

5. 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 ...

6. Gemstone - Wikipedia

   en.wikipedia.org/wiki/Gemstone

   Gemstone. Group of precious and semiprecious stones—both uncut and faceted—including (clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster. A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or ...

7. Chrysoberyl - Wikipedia

   en.wikipedia.org/wiki/Chrysoberyl

   Chrysoberyl. The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula Be Al 2 O 4. [ 5 ][ 6 ] The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different ...