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2. Quartzite - Wikipedia

   en.wikipedia.org/wiki/Quartzite

   Quartzite. Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone. [1][2] Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and ...

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. Baraboo Quartzite - Wikipedia

   en.wikipedia.org/wiki/Baraboo_Quartzite

   Baraboo Quartzite is a Precambrian geological formation [1] of quartzite, found in the region of Baraboo, Wisconsin. While pure quartzite is usually white or gray, Baraboo Quartzite is typically dark purple to maroon in color, due to the presence of iron (hematite) and other impurities. [2] Baraboo Quartzite may display strata created by ...

5. Chalcedony - Wikipedia

   en.wikipedia.org/wiki/Chalcedony

   Chalcedony. Chalcedony (/ kælˈsɛdəni / kal-SED-ə-nee, or / ˈkælsəˌdoʊni / KAL-sə-doh-nee) [2] is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. [3] These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic.

6. Sioux Quartzite - Wikipedia

   en.wikipedia.org/wiki/Sioux_quartzite

   Sioux Quartzite at Falls Park, Sioux Falls, South Dakota Cross-bedding in the Sioux Quartzite, Blue Mounds State Park, Minnesota, United States.. The Sioux Quartzite is a Proterozoic quartzite that is found in the region around the intersection of Minnesota, South Dakota, and Iowa, and correlates with other rock units throughout the upper midwestern and southwestern United States.

7. Amethyst - Wikipedia

   en.wikipedia.org/wiki/Amethyst

   Amethyst is a purple variety of quartz (SiO. 2) and owes its violet color to irradiation, impurities of iron (Fe3+. ) and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions. [2][3][4] The irradiation causes the iron Fe3+.