A large, single blocky prismatic crystal from Death Valley, California.
A group of Colemanite crystals from Death Valley, California.
CHEMISTRY - Ca2B6O11.5H2O
CRYSTALLOGRAPHY - Monoclinic
CRYSTAL GROWTH AND HABITS - Commonly forms prismatic to bladed crystals - typically with complex terminations. It can also be granular to massive.
COLOR AND OPTICAL PROPERTIES - Colorless to milky white or gray; yellowish white. It is transparent to translucent.
HARDNESS - 4.5
SPECIFIC GRAVITY - 2.4
LUSTER - Vitreous to adamantine
STREAK - White
BREAKABILITY - Very good cleavage along {010}, and good along {001}. Otherwise the fracture is sub conchoidal to uneven
OCCURRENCE - Colemanite is found associated with the playa lakes deposits. It forms by meteoric water acting on ulexite and borax.
ASSOCIATED MINERALS - Howlite, Ulexite, Gypsum, Borax, Calcite and Celestine.
MINERAL NAME - Colemanite was named after William Coleman who was the owner of the mine where the mineral was first found.