Most distinguishing features:Bladed habit, colour, and difference of hardness along and across cleavages
Other names/forms:Forsterite (Mg) and Fayalite (Fe)
Most distinguishing features:Pistachio-green colour and granular habit.
Industrial/economical uses:Peridote (a translucent variety of olivine) is considered a 'gem' mineral. Also used as a refractory sand and infrequently as an abrasive.