Ardealite
Ardealite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₂(PO₃OH)(SO₄)·4H₂O.
It crystallizes in the monoclinic crystal system (space group Cc). It is a member of the Gypsum structural group.
Key properties: specific gravity 2.34; optically biaxial.
IMA symbol Adl, grandfathered status — known before the IMA’s founding, named in 1932.
Found in limestone caves, as an early stage of the breakdown of bat guano, in reaction with calcite.
It is found associated with Brushite, gypsum, carbonate-hydroxylapatite, newberyite, taranakite.
The name comes from Ardeal, the old Romanian name for Transylvania.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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