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Name Origin | Herderite is named after S. A. W. von Herder, a mining official in Freiburg Germany |
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Chemical Formula | CaBePO4(F, OH) |
Color | Colorless, pale yellow, greenish white, pink, green |
Hardness | 5 - 5.5 on Mohs Scale |
Crystal System | Monoclinic, Crystals stout or prismatic; tabular; crusts |
Cleavage | Interrupted. Fracture conchoidal. Brittle |
Specific Gravity (SG) | 2.95 - 3.02 |
Pleochroism | None or weak |
Luster | Vitreous |
Occurrence |
Late stage hydrothermal mineral in granite pegmatites. |
Stone sizes |
Faceted gems from Maine are usually small. Brazil gems, however, have stronger color and maybe up to 25-30 carats from larger crystals |
Note: Herderite is a rare collector gem, especially in large sizes. It is too soft to wear, but attractive when cut. Clean stones are very hard to find. There is always the possibility of new and larger material coming on the market from Brazilian sources. It was first described in 1828 for an occurrence in the Sauberg Mine, Erzgebirge, Saxony, Germany.
References:
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
Photo credit:
"Herderite-mrz102a" by Rob Lavinsky, iRocks.com – CC-BY-SA-3.0. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Herderite-mrz102a.jpg#/media/File:Herderite-mrz102a.jpg
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
Photo credit:
"Herderite-mrz102a" by Rob Lavinsky, iRocks.com – CC-BY-SA-3.0. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Herderite-mrz102a.jpg#/media/File:Herderite-mrz102a.jpg