Massive
Datolite from the Delaware Mine, Keweenaw Peninsula, Michigan. The
Datolite has been colored by copper.
CHEMISTRY CaBSiO4(OH)
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Datolite crystals are commonly short prismatic or tabular. The crystals are usually complex. Datolite is also coarse to fine granular and found in compact masses.
COLOR AND OTHER OPTICAL PROPERTIES Datolite is colorless to white or lightly colored by impurities to greenish or pinkish hues. It is transparent to translucent.
HARDNESS 5 - 5.5
SPECIFIC GRAVITY 2.8 - 3.0
LUSTER Datolite has a vitreous luster but is dull in the massive varieties.
STREAK White
BREAKABILITY Conchoidal or uneven fracture, brittle
OCCURRENCE Datolite is a secondary mineral usually found in silica poor igneous rocks. It is also found in limestone skarns and schists.
ASSOCIATED MINERALS Chlorite, Calcite, Iron oxides, Zeolites