Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 millimeters or more. Such rocks are referred to as pegmatitic. Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite". Rarer "intermediate" and "mafic" pegmatite containing amphibole, Ca-plagioclase feldspar, pyroxene and other minerals are known, found in recrystallised zones and apophyses associated with large layered intrusions. Crystal size is the most striking feature of pegmatite, with crystals usually over 50mm in size. However, individual crystals over 10 meters across have been found, and the world's largest crystal was found within a pegmatite. Similarly, crystal texture and form within pegmatite may be taken to extreme size and perfection. Feldspar within pegmatite may display exaggerated and perfect twinning, exsolution lamellae, and when affected by hydrous crystallization, macroscale graphic texture is known, with feldspar and quartz intergrown. The mineralogy of a pegmatite is in all cases dominated by some form of feldspar, often with mica and usually with quartz, being altogether "granitic" in character. Beyond that, pegmatite may include most minerals associated with granite and granite-associated hydrothermal systems, granite-associated mineralization styles, for example greisens, and somewhat with skarn associated mineralization. It is however impossible to quantify the mineralogy of pegmatite in simple terms because of their varied mineralogy and difficulty in estimating the modal abundance of mineral species which are of only a trace amount. This is a consequence of the difficulty in counting and sampling mineral grains in a rock which may have crystals centimeters, decimeters or even meters acoss. Garnet, commonly almandine or grossular, is a common mineral within pegmatites intruding mafic and carbonate-bearing sequences.
Photographed by Michael P. Klimetz
WISCONSIN
Photographed by Michael P. Klimetz
Pegmatitic Diorite
SCOTLAND
Photographed by Michael P. Klimetz
Florence County
WISCONSIN
Tourmaline
Tourmaline
Quartz
Mica
Orthoclase
Photographed by Michael P. Klimetz
[With Almandine and Schorl Tourmaline]
Oxford County
MAINE
Almandine
Schorl
Photographed by Michael P. Klimetz
[With Muscovite and Schorl Tourmaline]
NEW HAMPSHIRE
Photographed by Michael P. Klimetz
[With Schorl Tourmaline]
MAINE
Photographed by Cheryl J. Moss, Mueser Rutledge Consulting Engineers
[Core]
Manhattan
NEW YORK
Photographed by Cheryl J. Moss, Mueser Rutledge Consulting Engineers
[Core]
Manhattan
NEW YORK
Photographed by Michael P. Klimetz
ALABAMA
Photographed by Michael P. Klimetz
[With Muscovite and Schorl Tourmaline]
SWITZERLAND
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Garnet]
White Plains Rest Stop
Hutchinson River Parkway
Rosedale
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Garnet]
White Plains Rest Stop
Hutchinson River Parkway
Rosedale
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Garnet]
White Plains Rest Stop
Hutchinson River Parkway
Rosedale
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Garnet]
White Plains Rest Stop
Hutchinson River Parkway
Rosedale
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Garnet]
White Plains Rest Stop
Hutchinson River Parkway
Rosedale
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite]
Kinkel Quarry
Bedford
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite]
Kinkel Quarry
Bedford
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite Pegmatite with Columbo-Tantalite and Triphylite]
Estes Pegmatite
West Baldwin
Cumberland County
MAINE
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Muscovite-Biotite Pegmatite with Minor Topaz in Hornblende-Biotite Gneiss]
Fordham Gneiss
Proterozoic
Yonkers
Westchester County
NEW YORK
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Garnet-Biotite Pegmatite with Columbite (Metallic Black)]
McKinney Mine
Spruce Pine
Mitchell County
NORTH CAROLINA
Photographed by Michael P. Klimetz
[Orthoclase-Quartz-Garnet-Biotite Pegmatite with Columbite (Metallic Black)]
