pegmatite noun. ['pɛgmǝtʌɪt] M19.
[Greek pēgmat-, pēgma thing joined together + -ITE¹.]
Geology. A coarsely crystallized rock commonly occurring in igneous intrusions, esp. dykes, and consisting mainly of feldspar and quartz.

■ pegmatitic [-'tɪtɪk] adjective resembling, consisting of, or having the structure of pegmatite L19.

■ pegmatoid noun & adjective (a rock) resembling or similar in structure to pegmatite L19.

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