Danburite is a calcium boron silicate typically occurring in contact metamorphic rocks. It is usually colorless but can be pale pink or yellow. It is named for Danbury, Connecticut (US) where it was first discovered in 1839.
CaB2(SiO4)2; Hardness 7 – 7.5; Orthorhombic
Quartz is a crystalline form of silica. The greatest concentrations of quartz are found in silica-rich igneous and metamorphic rocks. Quartz is one of Earth’s most abundant minerals and is an essential component of granite and many other rocks. Often transparent, Quartz can be found in almost any color. Quartz has piezoelectric properties, meaning it generates an electric charge in response to pressure.
SiO2; hardness 7; isometric.
Sphalerite is zinc sulfide, the chief ore of zinc. Variable amounts of iron can substitute for the zinc. It has a characteristic greasy luster, and is usually yellow to shades of brown. “Sphaleros” means “treacherous” as it was mistaken for galena yet yielded no lead when smelted.
ZnS; Hardness 3½ - 4; Isometric