Datolite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameDatolite
Chemical FormulaCaB(SiO4)(OH)
Mohs Hardness5.5
Crystal Systemmonoclinic
Lustervitreous
Streak Colorwhite
Cleavagepoor/indistinct on {001}
Fractureconchoidal
Specific Gravity2.95
Colorscolorless, white, pale green, yellow, pink, brown
Transparencytransparent
Type LocalityCharcas, Municipio de Charcas, San Luis Potosí, Mexico
Mineral GroupSilicates
Usescollector, gemstone
Associated Mineralsprehnite, epidote, calcite, zeolites, native copper
Rarityuncommon
Description
This specimen features well-formed, blocky to tabular crystals of pale yellowish-green datolite, exhibiting a distinct vitreous luster. The crystals are translucent to transparent, showcasing their characteristic monoclinic habit.
Geological Context
Datolite is typically found in hydrothermal veins, amygdules, and contact metamorphic zones, often associated with mafic igneous rocks such as basalt. It forms from the alteration of calcium-rich silicates in the presence of boron-bearing fluids.
