EPD Spark-2 test on APATITE rock sample: extracting crystals for gemstone processing and collections
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- čas přidán 23. 08. 2024
- Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca10(PO4)6(OH,F,Cl)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6F2 and Ca10(PO4)6Cl2.
Apatite is very common as an accessory mineral in igneous and metamorphic rocks, where it is the most common phosphate mineral. However, occurrences are usually as small grains which are often visible only in thin section. Coarsely crystalline apatite is usually restricted to pegmatites, gneiss derived from sediments rich in carbonate minerals, skarns, or marble. Apatite is also found in clastic sedimentary rock as grains eroded out of the source rock. Phosphorite is a phosphate-rich sedimentary rock containing as much as 80% apatite, which is present as cryptocrystalline masses referred to as collophane. Economic quantities of apatite are also sometimes found in nepheline syenite or in carbonatites.
Apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon-cut. Chatoyant stones are known as cat's-eye apatite, transparent green stones are known as asparagus stone,and blue stones have been called moroxite. If crystals of rutile have grown in the crystal of apatite, in the right light the cut stone displays a cat's-eye effect. Major sources for gem apatite are Brazil, Myanmar, and Mexico. Other sources include Canada, Czech Republic, Germany, India, Madagascar, Mozambique, Norway, South Africa, Spain, Sri Lanka, and the United States.
Apatite is occasionally found to contain significant amounts of rare-earth elements and can be used as an ore for those metals. This is preferable to traditional rare-earth ores such as monazite, as apatite is not very radioactive and does not pose an environmental hazard in mine tailings. However, apatite often contains uranium and its equally radioactive decay-chain nuclides.
The town of Apatity in the Arctic North of Russia was named for its mining operations for these ores.
Apatite is an ore mineral at the Hoidas Lake rare-earth project.
It is not so easy to recover in using common methods like mechanical crusher, jaw-crusher and etc.
There is a new approach to extract the mineral crystal from host rock - to strike them with a high voltage pulses in water.
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