WorldWide Drilling Resource

Frequently-Used Geological Terms Part 49 Glossary Adapted from the Dictionary of Geological Terms M Meta-Anthracite - Coal having a fixed carbon content of 98% or more; the highest rank of anthracite. Metabentonite - Metamorphosed, altered, or somewhat hardened bentonite, characterized by clay minerals (esp. illite) that no longer have the property of absorbing or adsorbing large quantities of water. The term has been applied to certain Ordovician clays of the Appalachian region and upper Mississippi River valley. Metacryst - A large crystal developed in a metamorphic rock by recrystal- lization, such as garnet or staurolite in mica schist. Metalliferous - Metal-bearing; specifically pertaining to a mineral deposit from which a metal or metals can be extracted by metallurgical processes. Metallogeny - The study of the genesis of mineral deposits, with emphasis on their relationship in space and time to regional petrographic and tectonic features of the earth’s crust. Metallurgy - The science and art of separating metals from their ores and preparing them for use, as by smelting and refining. Metamorphic Differentiation - A collec- tive term for the various processes by which minerals or mineral assemblages are locally segregated from an initially uniform parent rock during metamor- phism, e.g. garnet porphyroblasts in fine- grained mica schist. Metamorphism - The mineralogical, chemical, and structural adjustment of solid rocks to physical and chemical conditions imposed at depth below the surface zones of weathering and ce- mentation, which differ from the condi- tions under which the rocks originated. Metaquartzite - A quartzite formed by metamorphic recrystallization, as distin- guished from an orthoquartzite, whose crystalline nature is due to sediments becoming consolidated into rocks. Metasediment - A sediment or sedimen- tary rock showing evidence of having been subjected to metamorphism. Look for more terms next month! Metallurgy involves the production of alloys - the shaping, heat treatment, and surface treatment of the object. Above: casting bronze is an example of metallurgy. 57 WorldWide Drilling Resource ® APRIL 2016