Locations for Euclase

Euclase is found in four main geological environments, which I will list in order of how common they are: fluorine-rich pegmatite (typically YNF or intermediate Be-Ta-Li type), greisen/hydrothermal Sn-W-Mo rich veins, emerald bearing schists, and alpine clefts. Euclase localities are typically mined for other minerals such as topaz, aquamarine, emerald, or columbite-tantalite and produce Euclase crystals only as a byproduct.

By far, the most notable occurrences of fine Euclase crystals are in pegmatites where changing geochemical conditions leached beryllium out of beryl to form this mineral. Typically, these pegmatites are small, and fluorine enriched with simple mineralogy. Most of them have topaz closely associated with euclase. Notable localities of this type are the Alto do Giz pegmatite and nearby localities in Equador, Rio Grande do Norte, Brazil, pegmatites near Capelinha in the Jequitinhonha Valley, Minas Gerais, Brazil; St. Anne’s and Last Hope mines in Mwami, Mashonaland West, Zimbabwe; Chandler Mine, Raymond, New Hampshire, USA; and the Alto Ligonha District, Zambezia Province, Mozambique.

euclase_03Euclase also occurs with emeralds in schist or related hydrothermal veins in schists. These emerald-bearing schists are a very unique rock type in that they are derived from highly mafic to ultramafic protolith rock. Hydrothermal veins associated with these schists are related to faulting and metasomatism between the vein material and the schist. Beryllium in these veins is usually from a felsic rock intruding the schist whos fluids chemically leach the rock they travel through. In these environments, euclase is associated with beryl var. emerald, albite, apatite, bromellite, phenakite, chrysoberyl, pyrite, and calcite. Euclase from these types of deposits is more commonly blue than clear. Well known occurrences of Euclase associated with emeralds in mafic derived schist or mafic derived schist hosted hydrothermal veins are the emerald deposits of Colombia, especially those in the Cundinamarca Department and Malyshevo in Sverdlovskaya Oblast, which is located in the Ural Mountains of Russia.

Griesens and greisen-like hydrothermal veins with tin, tungsten, and molybdenum mineralization also host some occurences of euclase. Euclase forms in these rocks when incompatible rich fluids in granites rich in incompatible elements boil up through the granite and sometimes into the country rock. In these environments, Euclase ais typically associated with micas such as muscovite or zinnwaldite, quartz, fluorite, beryl, scheelite, cassiterite, molybdenite, and wolframite. Localities that are examples of this are the Piaotang Mine in Jiangxi Province, China, Cligga Head, Cornwall, England, and the Raduga Be deposit in the remote Sayan Mountains, Krasnoyarskii Kray, Russia.

The least abundant occurrence of euclase is in alpine clefts. Here, it occurs with quartz, adularia, rutile, chlorite, fluorite, and titanite. Crystals from these types of environments tend to always be clear and small- only rarely do they get larger than a centimeter. Salzburg and Tyrol, Austria are likely the best occurrence of euclase in this kind of environment.

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