Dellaite
Dellaite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₆(Si₂O₇)(SiO₄)(OH)₂.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: specific gravity 2.975; optically biaxial.
IMA symbol Dll, IMA status: approved, named in 1964.
Found in late-stage, fracture-controlled replacement veins cutting thermally metamorphosed limestones (Scotland). A late-stage hydration product of pre-existing skarn minerals in a silica- deficient environment (Japan).
It is found associated with Calcite, spurrite, kilchoanite, foshagite, tilleyite (Scotland); bicchulite, vesuvianite, calcite, clintonite, magnetite, sphalerite (Japan); hillebrandite.
The mineral was named to honor Della Martin Roy (b. 1926), Pennsylvania State University, University Park, Pennsylvania, USA.