WorldWide Drilling Resource

Frequently-Used Geological Terms Part 45 Glossary Adapted from the Dictionary of Geological Terms M Maceral - One of the organic constituents that comprise coal mass. Macerals are to coal, as minerals are to inorganic rock. Maceration - The process of disintegrating sedimentary rocks such as coal and shale, to extract and concentrate acid-insoluble microfossils. It includes mainly chemical treatment by oxidants and alkalies which will remove extraneous mineral and organic constituents. Mafic - Igneous rock composed primarily of dark, ferromagnesian minerals. Magnesia - Magnesium oxide. Magnesian Limestone - Limestone containing appreciable magnesium having at least 90% calcite and no more than 10% dolomite. Magnesite - A white to gray mineral usu- ally found as earthy masses or irregular veins. It is used in making refractory magnesia. Magnetite - A black, isometric, strongly magnetic opaque mineral. It often contains titanium oxide and it constitutes an impor- tant ore of iron. Magnetite is a very com- mon and widely distributed accessory mineral in rocks of all kinds. Magnetometer - An instrument used to measure the earth’s magnetic field and its changes. Malachite - A bright green mineral. It is a minor ore of copper and a common sec- ondary mineral associated with azurite in the oxidized zone of copper sulfide de- posits. Manganese Nodule - An irregular potato shaped mass of manganese-rich material which occurs on the ocean floor. Manganite - A gray to black orthorhom- bic mineral. It is an ore of manganese. Mantle - The zone of earth below the crust and above the core. It is divided into the upper mantle and lower mantle with a transi- tion zone in between. Manto - A flat lying, bedded deposit; either a sedimentary bed or a replacement strata- bound ore body. Marble - Ametamorphic rock consisting of fine- to coarse-grained recrystallized cal- cite and/or dolomite. WWDR photo of magnetite from Pershing County, Nevada. More terms to come next month! - $&(12$0$# 0& -(8 2(.- .6 9 .-* 5 6 , (+ 1 +$1 2'0../0."*!(2 "., 555 2'0../0."*!(2 "., +3$ (1 -.2 )312 /0("$ !32 2'$ .4$0 ++ 1$04("$ -# $6/$0($-"$ .%%$0$# !7 '0../ ."* (2 .,/ -7 21 WorldWide Drilling Resource ® DECEMBER 2015