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Gabbro often contains valuable amounts of chromium, nickel, cobalt, gold, silver, platinum, and copper sulfides.
Ocellar varieties of gabbro are often used as ornamental facing stones, paving stones and it is also known by the trade name of 'black granite', which is a popular type of graveyard headstone used in funerary rites. It is even more popular now for use in kitchens and their countertops, also under the misnomer of 'black granite'. Note that the term "granite" is widely but wrongly applied to almost any polished surfacing stone. http://en.wikipedia.org/wiki/Gabbro
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The primary economic value of anorthosite bodies is the titanium-bearing oxide ilmenite. However, some Proterozoic anorthosite bodies have large amounts of labradorite, which is quarried for its value as both a gemstone and a building material. Archean anorthosites, because they are calcium-rich, have large amounts of aluminium substituting for silicon; a few of these bodies are mined as ores of aluminium.
Anorthosite was prominently represented in rock samples brought back from the Moon, and is important in investigations of Mars, Venus and meteorites. http://en.wikipedia.org/wiki/Anortho...
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Ultramafic (or ultrabasic) rocks are igneous and meta-igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is considered to be composed of ultramafic rocks.
Ultramafic rocks and the regolith
Where ultramafic rocks (in particular, the types which have low amounts of nutrient elements such as calcium, potassium and phosphorus) are exposed on the surface, the high metal content of the rocks creates unique vegetation. Examples are the ultramafic woodlands and ultramafic barrens of the Appalachian mountains and piedmont, the "wet maquis" of the New Caledonia rain forests, and the ultramafic forests of Mount Kinabalu and other peaks in Sabah, Malaysia. Vegetation is typically stunted, and is sometimes home to endemic species adapted to the metallic soils.
Often thick, magnesite-calcrete caprock, clayey laterite and duricrust forms over ultramafic rocks in tropical and subtropical environments. Particular floral assemblages associated with highly nickeliferous ultramafic rocks are indicative tools for mineral exploration.
Weathered ultramafic rocks may form lateritic nickel ore deposits.
http://en.wikipedia.org/wiki/Ultramafic
