Definition
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Etymology
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Teschenite is coarse- to fine-grained, dark-coloured intrusive igneous rock that usually occurs in sills, dikes and irregular masses and is always altered to some extent
From its occurrence near Teschen. now known as Cieszyn, Pol., Scotland
Coarse Grained Rock, Opaque Rock
Essexite which is also known as nepheline monzogabbro, is a dark gray or black holocrystalline plutonic Iigneous Rock
From the locality in Essex County, Massachusetts,US
Fine Grained Rock, Opaque Rock