Tilasite
Tilasite is an arsenate mineral gemstone, with the elemental formula CaMgF. It prefers the monoclinic form of crystal, and has Mohs [scale of mineral hardness|Mohs] hardness of 5. It was named in 1895 by Hjalmar Sjögren in honor of Daniel Tilas, who was once director of mines for Sweden, and a regional governor for Västmanland. It was first discovered in Langban, Varmland.
In 1972, Bladh et al. characterised samples found near Bisbee, Arizona.
In 1994, Bermanec discovered centro-symmetric Tilasite near Nezhilovo, North Macedonia.