Outstanding vitreous colorless crystals of the very rare mineral hyalotekite from one of the only 3 known localities worldwide: Artillery Peak, Artillery Mountains, Mohave County, Arizona, United States of America. Associated to minoritary blue kinoite. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Hyalotekite
Hyalotekite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ba,Pb,K)₄(Ca,Y)₂(B,Be)₂(Si,B)₂Si₈O₂₈F.
It crystallizes in the triclinic crystal system (space group I-1). It is a member of the Hyalotekite structural group.
Key properties: Mohs hardness 5–5.5; specific gravity 3.81–3.82; Vitreous to greasy luster; optically biaxial.
IMA symbol Hya, grandfathered status — known before the IMA’s founding, named in 1877.
Sparingly in feldspar in a metamorphosed Fe{Mn deposit (Lº angban, Sweden); in reedmergnerite pegmatite in an alkaline massif (Dara-i-Pioz massif, Tajikistan).
It is found associated with Quartz, calcite, hematite, barylite, barite, manganoan pectolite, ferrian potassic feldspar, calderitic andradite, melanotekite, barian hedyphane.
Its name comes from the Greek for glass and to melt, in allusion to its easy fusibility.