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Michel-Lévy interference colour chart issued by Zeiss Microscopy. In optical mineralogy, an interference colour chart, also known as the Michel-Levy chart, is a tool first developed by Auguste Michel-Lévy to identify minerals in thin section using a petrographic microscope.
Pleochroism is an extremely useful tool in mineralogy and gemology for mineral and gem identification, since the number of colors visible from different angles can identify the possible crystalline structure of a gemstone or mineral and therefore help to classify it. Minerals that are otherwise very similar often have very different pleochroic ...
In 1986, California named benitoite as its state gemstone, a form of the mineral barium titanium silicate that is unique to the Golden State and only found in gem quality in San Benito County. [80] ^ Colorado is the only state whose geological symbols reflect the national flag's colors: red (rhodochrosite), white (yule marble), and blue ...
An achromatic gray is a gray color in which the red, green, and blue codes are exactly equal. The web colors gray, gainsboro, light gray, dark gray, and dim gray are all achromatic colors. A chromatic gray is a gray color in which the red, green, and blue codes are not exactly equal, but are close to each other, which is what makes it a shade ...
Amethyst (purple variety of quartz) Ametrine (variety of quartz) Ammolite (organic; also a gemstone) Amosite (asbestiform grunerite) Antozonite (variety of fluorite) Anyolite (metamorphic rock - zoisite, ruby, and hornblende) Aquamarine (light blue variety of beryl) Argentite (high temperature form of acanthite) Asbestos (fibrous serpentine- or ...
This color scheme is caused by the oxidation of iron. Iron leached from rocks provides the pigment that gives the gemstone its beautiful array of colors. The concentration of iron and the amount of oxidation determine the color within or between an agate's bands. There can also be white, grey, black, and tan strips of color as well.
As amethyst is readily available in large structures, the value of the gem is not primarily defined by carat weight. This is different from most gemstones, since the carat weight typically exponentially increases the value of the stone. The biggest factor in the value of amethyst is the color displayed. [41]
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 .