Gem, Rock, and Mineral Postage Stamps Featuring
Basalt

Rock Name:	Basalt
Composition:	A fine-grained, igneous rock formed when lava flows or erupts onto the surface of the earth and cools rapidly. Contains less than 53% silica. Commonly contains olivine, plagioclase, and pyroxene.
Industrial Uses:	Crushed stone.
Additional Notes:	Basalt is the most common rock type in the Earth's crust. The magma from which basalt forms is most frequently produced by direct melting of the Earth's mantle. Shield volcanos, such as those that make up the Hawaiian islands, are composed almost entirely of basalt.


Diabase (Doleritic Basalt) Afars & Issas Scott 349 10 francs 22 Nov 1971	Olivine Basalt Afars & Issas Scott 350 15 francs 8 Oct 1971

Scott 349 and 350 show thin-sections of rocks viewed under polarized light.