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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.
Minerals with an acicular habit include mesolite, natrolite, [2] malachite, gypsum, rutile, brochantite and bultfonteinite. Crystals of dimethyltryptamine have an acicular habit, [3] but this substance is not regarded as a mineral by the International Mineralogical Association. A acicular phase of steel is bainite.
Rutile is an oxide mineral composed of titanium dioxide (TiO 2), the most common natural form of TiO 2. Rarer polymorphs of TiO 2 are known, including anatase , akaogiite , and brookite . Rutile has one of the highest refractive indices at visible wavelengths of any known crystal and also exhibits a particularly large birefringence and high ...
Creedite is a calcium aluminium sulfate fluoro hydroxide mineral with formula: Ca 3 Al 2 SO 4 (F,OH) 10 ·2(H 2 O). Creedite forms colorless to white to purple monoclinic prismatic crystals. It often occurs as acicular radiating sprays of fine prisms. It is translucent to transparent with indices of refraction of n α = 1.461 n β = 1.478 n γ ...
The crystals are vitreous and vary in color from brown, blue, and green to more rare violet and pink. Substitution of iron and other tri-valent elements for aluminium result in the color variations. It has a Mohs hardness of 7 and a specific gravity of 3.3 to 3.4. Crystals show pleochroism from red to blue to violet.
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.
Phantom crystal of 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 ...
Prasiolite (also known as green quartz, green amethyst or vermarine) is a green variety of quartz. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, [ citation needed ] but it has also been mined in the Lower Silesia region of Poland .