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2. Rutilated quartz - Wikipedia

   en.wikipedia.org/wiki/Rutilated_quartz

   Rutilated quartz used as a gemstone. Rutilated quartz is a variety of quartz which contains acicular (needle-like) inclusions of rutile. [1] It is used for gemstones. These inclusions mostly look golden, but they also can appear silver, copper red or black. The inclusions may be distributed randomly or in bundles, which sometimes are arranged ...

3. Rutile - Wikipedia

   en.wikipedia.org/wiki/Rutile

   Rutile is a common accessory mineral in high-temperature and high-pressure metamorphic rocks and in igneous rocks. Thermodynamically, rutile is the most stable polymorph of TiO 2 at all temperatures, exhibiting lower total free energy than metastable phases of anatase or brookite. [7] Consequently, the transformation of the metastable TiO 2 ...

4. Herkimer diamond - Wikipedia

   en.wikipedia.org/wiki/Herkimer_diamond

   Herkimer diamonds are double-terminated quartz crystals discovered within exposed outcrops of dolomite in and around Herkimer County, New York, and the Mohawk River Valley in the US. [1][2] They are not diamonds; the "diamond" in their name is due to both their clarity and well formed faces. Because the first discovery sites were in the village ...

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. Phantom quartz - Wikipedia

   en.wikipedia.org/wiki/Phantom_quartz

   Phantom quartz. Phantom quartz is a variety of quartz consisting of visible layers of overlapping crystal growths. The outline of the inner crystals can be seen due to some variation in composition or mineral inclusion making the boundary between growths visible. [1] The interior crystal layers are known as phantoms. Phantoms can be found in ...

7. Acicular (crystal habit) - Wikipedia

   en.wikipedia.org/wiki/Acicular_(crystal_habit)

   Acicular, in mineralogy, refers to a crystal habit composed of slender, needle-like crystals. Crystals with this habit tend to be fragile. Complete, undamaged acicular specimens are uncommon. Needle-shaped acicular millerite crystals on white quartz. The term "acicular" derives from the Late Latin "acicula" meaning "little needle". [1]