Ardealite

Formula:  Ca₂(SO₄)(HPO₄)^.4H₂O

Origin of name:  Locality; Ardeal, old Romanian name for Transylvania

Crystal system:  Monoclinic

Crystal class:  m

Twinning:

Unit cell: a = 5.721 Å, b = 30.992 Å, c = 6.250 Å, b = 117.26°

Colour:  Pale yellow, yellow, brownish yellow, colourless

Diaphaneity: Semitransparent

Luster:

Habit:  Very fine-grained powdery masses and crusts

Hardness:

Specific gravity:  2.34

Cleavage: 

Tenacity:

Streak: White

Synonyms/varieties:

Comments Found in limestone caves, as an early stage of the breakdown of bat guano, in reaction with calcite