Metamorphosed aluminous sedimentary rocks.
Common world wide occurrences.
From the Greek, stauros - "cross" and lithos - "stone" in allusion to the common cross shaped twins of the crystals.
brownish yellow, brownish black, yellow brown, dark brown, or reddish brown.
3.65 - 3.77, Average = 3.71
Translucent to opaque
Tabular - Form dimensions are thin in one direction., Twinning Common - Crystals are usually twinned.,
Vitreous - Dull