Ca3(SO3)2(SO4) · 12H2O IMA 1990
Orschallite, one of the rarest minerals in volcanic Eifel region.
‘Type locality and so far the only place where orschallite was found is the Hannebacher Ley. It occurred here in small pores in a dense area of the melilite nepheline leucitite. The well-developed, colorless, transparent and clear crystals have a cubic shape. Their crystol form is trigonal. The slight deviations from the right angles cannot be seen macroscopically. However, they are rhombohedral. Sometimes the pole edges are also truncated by narrow surfaces of the negative rhombohedron.’ quoted by Günter Blaß (for more details see Eifel CD)
Orschallite was only been found in a few specimens at the site and is accordingly to be regarded as an extreme rarity. The second sulphite-containing mineral, hannebachite, which occurs in the same rock, is much more common.
Found by F.J.Emmerich, collection & photo © 2021 by Volker Heck