Noun
An eruptive rock characterized by the presence of chrysolite (peridot). It also usually contains pyroxene, enstatite, chromite, etc. It is often altered to serpentine.
Source: Webster's dictionaryXenoliths of garnet peridotite have been carried up from depths of convert and greater by kimberlite, and garnets from such disaggegated xenoliths are used as a kimberlite indicator minerals in diamond prospecting. Source: Internet
Hence, garnet peridotite must have been formed at great depth in the earth. Source: Internet