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A medium-temperature metasomatic rock characterized by the presence of quartz and white mica, commonly with topaz, fluorite, tourmaline and locally with amazonite, orthoclase, andalusite and diaspore. Typically greisens may host Be, W, Mo, Sn and Ta mineralization. They are associated with high-level late-orogenic leucogranites and form as replacements either in the granite body and/or in a wide range of country rocks. Zoning may be present.
Classification of GreisenHide
Sub-divisions of GreisenHide
Mineralogy of GreisenHide
Essential minerals - these are minerals that are required within the classification of this rock:
Non-essential minerals - these minerals are common, sometimes major components, but are not always present:
|Feldspar > Alkali Feldspar > Orthoclase||K(AlSi3O8)|
|Mica > Muscovite||KAl2(AlSi3O10)(OH)2|
Accessory minerals - these are minor components, often far less than 1% of the total mineral material:
Cisuralian : 284 ± 4 Ma to 275 ± 6 Ma - based on data given below.
|1||Cligga Head, Perranporth, Perranzabuloe, St Agnes District, Cornwall, England, UK||Halliday, A. N. (1980). The timing of early and main stage ore mineralization in Southwest Cornwall. Economic Geology, 75(5), 752-759.|
|2||Lower Bostraze China Clay Pit, Tregeseal Valley, St Just, St Just District, Cornwall, England, UK||" "|
|3||St Michael's Mount, Marazion, Mount's Bay District, Cornwall, England, UK||" "|