Distinctive features:  
Greenish colour when fresh, medium brown when weathered. Texture and composition.

Colour: 
Olive green when fresh, but weathering to dark ochre brown due to the formation of iron oxides.

Texture and granularity: 
Granular -- saccharoidal.

Composition: 
Made up almost entirely of small grains of olivine, or pyroxene may be present iin appreciable amounts.

Field associations: 
As small intrusions, sills and sykes. Often brought to the surface from a great depth by volcanic activity (olivine nodules in basalt).

Varieties:
Dunite, which is composed of olivine only and is a pistachio green colour, and picrite, which is composed of olivine plus subordinate amounts of plagioclase and is pale green. Note: Pyroxenite, which consists only of pyroxene, is black and has a 90 degree cleavage, and hornblendite, which consists only hornbledne, is black and has a 120 degree clevage.

 

Worldwide, but particularly in New Zealand, USA (New York, Kentucky, Georgia, Arkansas, Carolina and lesser amounts in other states).

 

As a source of valuable ores and minerals, including chromite, platinum, nickel and precious garnet. Diamonds are obtained form mica-rich peridotite (kinmberlite) in South Africa.