Definition of "pegmatite" []

• A coarse-grained granite, sometimes rich in rare elements such as uranium, tungsten, and tantalum. (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.

• "Coarse granite (known as pegmatite) often breaks up in weathering, leaving large pieces of quartz and feldspar lying on the ground."
• "In most rocks feldspar is in too small grains and is too intimately associated with other minerals to be of commercial importance; in only one type of rock, pegmatite, which is an igneous rock of extremely coarse and irregular texture, are the feldspar crystals sufficiently large and concentrated to be commercially available."
• "Whitmore owns the Palermo mines in North Groton, N.H., a source of the granite-type rock known as pegmatite, as well as about 150 other minerals including whitmoreite, named in his honor."