from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A coarse-grained granite, sometimes rich in rare elements such as uranium, tungsten, and tantalum.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A coarsely crystalline igneous or plutonic rock composed primarily of feldspar and quartz, normally with muscovite and/or biotite mica. Often contains other minerals, which may be of economic importance. Pegmatite is chemically identical to granite, but has a much coarser crystal structure. Common colors are gray, white, and pink. Pegmatite is quarried for decorative stone and as a source of beryllium, columbium and tantalum when these are present. Gemstones of the quartz/silicate family may also be found in pegmatites.
from the GNU version of the Collaborative International Dictionary of English
- n. Graphic granite. See under granite.
- n. More generally, a coarse granite occurring as vein material in other rocks.
from The Century Dictionary and Cyclopedia
- n. Coarsely crystallized granite. Also called granitel, granitelle.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a form of igneous rock consisting of extremely coarse granite resulting from the crystallization of magma rich in rare elements
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.
The largest spodumene crystal ever found was found in a pegmatite in South Dakota.
Commercial quantities of spodumene are in a special igneous rock deposit that geologists call a pegmatite.
This mineral is typical of a special igneous rock known as a pegmatite.
Very large sheets or crystals of muscovite form in a pegmatite.
A pegmatite is an extremely slow-cooling igneous rock in which very large crystals can form.
The most important sources of sheet mica are the pegmatite deposits.
Both of these minerals are typical of a special igneous deposit known as a pegmatite.