Pegmatoid vs. Pegmatite — What's the Difference?

(mineralogy) Resembling pegmatite

A pegmatite is an igneous rock, formed by slow crystallization at high temperature and pressure at depth, and exhibiting large interlocking crystals usually greater in size than 25 mm (0.98 in). Most pegmatites are intrusive rocks found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths.The word pegmatite derives from Homeric Greek, πήγνυμι (pegnymi), which means “to bind together”, in reference to the intertwined crystals of quartz and feldspar in the texture known as graphic granite.Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition as granite.

Such a mineral

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

Resembling pegmatite; pegmatic.

A coarsely crystalline igneous or plutonic rock composed primarily of feldspar and quartz, normally with muscovite and/or biotite mica.

Graphic granite. See under Granite.

A form of igneous rock consisting of extremely coarse granite resulting from the crystallization of magma rich in rare elements