WorldWide Drilling Resource

Frequently-Used Geological Terms Part 54 Glossary Adapted from the Dictionary of Geological Terms M Molybdate - A mineral compound in which the hexavalent molyb- denum ion and the four oxygens form a flattened square rather than a tetrahedron. Tungsten and molybdenum many substitute for each other. Molybdenite - A lead gray hexagonal mineral. It is the principal ore of molybdenum. Molybdenite typically occurs in foliated masses or scales, and is found in pegmatite dikes and quartz veins. It resem- bles graphite in appearance and to the touch, but has a bluer color. Monazite - Ayellow or brown monoclinic mineral. It is considered a rare earth phosphate. It is the main source of the rare earth element thorium. Monomineralic - Term used to describe a rock composed wholly (or almost wholly) of a single mineral. Morphometry - The measurement and mathematical analysis of the configuration of the earth’s surface, and of the shape and dimensions of its landforms. Mortar Structure - A structure, presum- ably cataclastic, in granites and gneisses in which small crushed grains of quartz and feldspar occupy the interstices be- tween larger individuals, resembling stones set in mortar. Mother Lode - A main mineralized unit which may not be economically valuable in itself, but to which workable veins are related. Also refers to an ore deposit from which a placer is derived. Muck - Dark decomposed organic matter, intermixed with a high percentage of silt. The term is also used to describe waste rock in mining. Mud Engineer - A specialist who studies and prescribes the materials, chemicals, and proprietary additives used to make and maintain the properties of the drilling mud used in rotary drilling. Mud Pot - A type of hot spring containing boiling mud, usually sulfurous and often multicolored, as in a paint pot. Mud pots are commonly associated with geysers and other hot springs in volcanic areas. Mud Pump - The reciprocating pump used to impel drilling mud through the essentially closed circulating system used in rotary drilling. Musical Sand - A sounding sand which emits a definite musical note or tone when stirred, trodden on, or otherwise disturbed. Also called whistling sand. Look for more terms next month! The Great Sand Dunes National Park in Colorado, experiences musical sand during avalanches. Photo courtesy of NPS. 29 WorldWide Drilling Resource ® OCTOBER 2016