WorldWide Drilling Resource

45 SEPTEMBER 2022 WorldWide Drilling Resource® Frequently-Used Geological Terms Part 95 Glossary Adapted from the Dictionary of Geological Terms S Slate - 1. A compact, fine-grained metamorphic rock that possesses slaty cleavage, and hence can be split into slabs and thin plates. Most slate was formed from shale. 2. A coal miner’s term for any shale accompanying coal. Slickenside - A polished and striated rock surface resulting from friction along a fault plane. Slim Hole - 1. A rotary borehole having a diameter of five inches or less. 2. A drill hole of the smallest possible size, often drilled with a truck-mounted rig, used primarily for mineral exploration or to obtain stratigraphic or structural information. Sluicing - Concentrating heavy minerals, such as gold or cassiterite, by washing unconsolidated material through boxes (sluices) equipped with riffles that trap the heavier minerals on the floor of the box. Slurry - Ahighly fluid mixture of water and finely divided material, mostly of pulverized coal and water for movement by pipeline, or of cement and water for use in grouting. Slush Pit - A surface excavation or diked area to impound water or drilling mud for use in drilling or to retain fluids discharged from a well. Smectite - A group of swelling clay minerals which are the main components of bentonite and fuller’s earth; common in soils, sedimentary rocks, and some mineral deposits. Soapstone - 1. Amassive metamorphic rock composed essentially of talc, with varying amounts of micas, chlorite, and other minerals. 2. A mining and drilling industry term for any soft rock with a greasy or soapy feel. Sodium Bentonite - High-swelling sodium montmorillonite clay widely used in well drilling muds, pelletizing iron ore, and bonding foundry sands; also known as Wyoming bentonite. Soft Ground - Portion of amineral deposit which can be mined without drilling and blasting; usually the upper, weathered portion of the deposit. Solution mining - Mining of soluble rock material, especially salt, from underground deposits by pumping water down wells into the deposit and removing brine created through the process. Sonde - Elongated cylindrical tool assembly lowered into a borehole and used to acquire a well log. EXB Slickensides in Utah, courtesy of the U.S. Geological Survey. Look for more terms soon!