Any of various altered basic igneous rocks colored green by chlorite, hornblende, or epidote.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "greenstone" in a sentence
"The soils of the Marcassin vineyard are 18–24 inches of gravelly loam over highly fractured rock of marine volcanic origin, known as greenstone or basalt."
"Expedition brought back specimens of free gold found in basalt, apparently eruptive, and in corundophyllite, which the engineer called greenstone porphyry: silver appeared in the red sands, in the chloritic quartz, and in the titaniferous iron of the Jebel el-Abayz; the value being 265 to 300 francs per ton, with traces in the scoriæ."
"MCKELLEN: This is greenstone, which is unique to New Zealand."