BiotiteBiotite is a very common form of mica. It is named in honor Jean Baptiste Biot (1774 - 1862), a French physicist, mathematician, and astronomer who researched the mica minerals for their optical properties. Because of Biotite's abundance, its presence is usually lacking in collections except for it being an accessory mineral to other minerals. Biotite can come in enormous crystal sheets that can weigh several hundred pounds. Thin sheets can be peeled off as layers, and the thinner a layer is peeled the greater its transparency becomes.
In 1998, the IMA removed the status of Biotite as an individual mineral species, and instead declared it as a group name for the following individual members: Phlogopite, Annite, Siderophyllite, and Eastonite. However, mineral collectors still refer to Biotite by its traditional name and rarely make a distinction among its members except for Phlogopite. Biotite is very hard to clean because if washed it will absorb water internally and start to break apart. The best way to wash Biotite and other Micas is with a dry electric toothbrush. http://www.minerals.net/mineral/biotite.aspx KaoliniteKaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O5(OH)4. It is a layeredsilicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra.[4] Rocks that are rich in kaolinite are known as kaolin or china clay.[5]
The name is derived from Kao-ling (Chinese: 高岭/高嶺; pinyin: Gaoling), a village near Jingdezhen, Jiangxi province, China.[6] The name entered English in 1727 from the French version of the word: "kaolin", following Francois Xavier d'Entrecolles's reports from Jingdezhen.[7] In Africa, kaolin is sometimes known as kalaba (in Gabon[8] and Cameroon[9]), calaba, and calabachop (in Equatorial Guinea). Kaolinite has a low shrink-swell capacity and a low cation exchange capacity (1-15 meq/100g). It is a soft, earthy, usually white mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminium silicate minerals like feldspar. In many parts of the world, it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow or light orange colors. Alternating layers are sometimes found, as at Providence Canyon State Park in Georgia, United States. Commercial grades of kaolin are supplied and transported as dry powder, semi-dry noodle or as liquid slurry. http://webmineral.com/data/Kaolinite.shtml LepidoliteLepidolite is a lithium-rich mica known for its pink and lilac colors. It is a common matrix mineral to Tourmaline and Quartz, providing them with a very aesthetic and glittery base. A pink variety of the related mica mineral Muscovite can be identical in appearance to Lepidolite, and is many times incorrectly labeled as Lepidolite.
http://www.minerals.net/mineral/lepidolite.aspx MuscoviteMuscovite is the most common form of mica. Its name is derived from "Muscovy Glass", which describes thick sheets of transparent mica that were once used as a glass substitute in Russia. Because of Muscovite's abundance, its presence is usually lacking in collections except for it being an accessory mineral to other minerals. However, there are certain interesting formations and colors which are very aesthetic, and those forms are well-represented in collections. Muscovite can come in enormous crystal groupings that can weigh several hundred pounds. Thin sheets can be peeled off as layers, and the thinner a layer is peeled the greater its transparency becomes.
Except for large and resistant specimens, Muscovite is very hard to clean because if washed it will absorb water internally and start to break apart. The best way to wash Muscovite and other Micas is with a dry electric toothbrush. http://www.minerals.net/mineral/muscovite.aspx TalcTalc is known for being the softest mineral on earth. It is number 1 on the Mohs hardness scale, and can be easily scratched by a fingernail. Talc is not commonly seen in collections, as it is usually uninteresting and fairly common, although a few deeply colored and crystallized examples are known and well sought after. Also very popular are the Talc pseudomorphs. Talc forms some very interesting pseudomorphs after many different minerals, and certain localities are known for the specific minerals replaced by Talc.
Health concerns including a rare respiratory disease are known to be associated with Talc in its powder form. Although solid forms of Talc are assumed to be safe, and most concerns are only after prolonged exposure, it is advisable to wash hands after handling Talc. http://www.minerals.net/mineral/talc.aspx |
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