White crystal aggregates of the very rare mineral killalaite from the TL in Killala, Ireland, in a dark contrasting matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Killalaite
Killalaite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₆.₄[H₀.₆Si₂O₇]₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/m).
Key properties: specific gravity 2.94; optically biaxial.
IMA symbol Kil, IMA status: approved, named in 1973.
Found as a secondary mineral in cavities and veins in hydrothermally altered and thermally metamorphosed limestones.
It is found associated with Calcite, afwillite, spurrite, wollastonite (Killala Bay, Ireland); larnite, magnetite, perovskite, spinel, spurrite (Carneal, Ireland).
The name is derived from the locality at Killala Bay, Ireland.