Igneous rocks are classified on the basis of their composition and their texture. Magma, and the igneous rock it becomes, has a range of chemical compositions. For example, basalt is a mafic lava flow rock which originates from melting of the upper mantle.
the action of forming or process of being formed.
"the formation of the Great Rift Valley"
the nature of something's ingredients or constituents; the way in which a whole or mixture is made up.
"the social composition of village
the feel, appearance, or consistency of a surface or substance.
"skin texture and tone"
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