The Mines and Minerals of Lavrion - AlpersiteLast Updated: 4th Feb 2020
By Branko Rieck
ALPERSITE, (Mg,Cu)(SO4) · 7H2O, monoclinic
The mineral alpersite is easily overlooked because it is often similar in color and other physical properties to chalcanthite and copper-bearing melanterite. Depending on the amount of copper impurities its color ranges from colorless to sky blue. It looks remarkably like the aubertite-magnesioaubertite solid solutions found at the Plaka Sulfate Locality. Unfortunately, it is near impossible to conserve it for an extended period of time. From experience it can be said that alpersite decomposes within hours to copper-bearing pentahydrite if it is removed without any precautions from the mine environment. If it is enclosed and sealed in an air-tight container directly at the place of discovery, at least two months later it was still possible to find remains of alpersite with PXRD. Long-time conservation is probably only possible by enclosing the specimen in synthetic resin directly after removal from the host rock (I have an ongoing long-term experiment in this direction).
Alpersite is found as grainy, light blue coating on matrix that also hosts “rams’ horn” epsomite up to 10 cm in size. Individual grains reach half a millimeter in size.
Initially, alpersite was found at the lower (ancient) level of the Esperanza mine where it is locally abundant. Samples collected in spring 2019 under controlled conditions showed, that alpersite also occurs at many locations in the Villia and Dipseliza areas.
Fig. 1: This specimen was recovered from the mine in an airtight container. After photography it was re-sealed. The next day PXRD proved the material to be alpersite. Two weeks later PXRD showed only the presence of pentahydrite with no more alpersite detectable. The white fibers are chemically similar to alpersite: epsomite.
Thanks go to Dr. Uwe Kolitsch for constructive comments and diligent proofreading to improve this article.
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