WorldWide Drilling Resource

7 WorldWide Drilling Resource ® SEPTEMBER 2018 Frequently-Used Geological Terms Part 74 Glossary Adapted from the Dictionary of Geological Terms Q Quaquaversal - Said of strata and structures which dip outward in all directions from a central point. The term also refers to a geological structure which has a quaquaversal dip such as a dome. Quarry - Open workings, usually for the extraction of stone. Quartz - Crystalline silica and an important rock-forming mineral, quartz is one of the most common minerals. It occurs in transparent hexagonal crystals, crystalline, or cryptocrystalline masses. Quartz is a 7 on the Mohs Hardness Scale. Quartzarenite - A sandstone composed primarily of quartz. The term is equivalent to orthoquartzite. Quartz Crystal - Quartz which is transparent or nearly so. In ad- dition to being colorless, it also has a low refractive index resulting in low brilliance. It is used for lenses, wedges ( see Quartz Wedge ), and prisms in optical instruments. It is also used for frequency con- trol in electronics. Quartz Index - A derived quantity in the Niggli system of rock clas- sification which is an indicator of a rock’s degree of silica saturation. Also refers to the measure of the miner- alogical maturity of a sandstone. It is expressed as the ratio of quartz plus chert, to the combined percentage of feldspar, rock fragments, and clay matrix. It is used as a basis for evaluating the degree of weathering of the source rock and the degree to which the sediment has been transported. Quartz Wedge - An elongated wedge of clear quartz used in the analysis of a mineral’s fast and slow vibrational directions under the polarizing microscope. Quicksilver - A term applied to mercury where it occurs as a native mineral or has been mined but not yet used. Look for more terms next month! WWWWDDRR photo of the Capital Quarries Rolla, Missouri, quarry. EXB