WorldWide Drilling Resource

Announcing the 53 rd Annual Shallow Exploration Drillers Clinic! April 17 - 18, 2018 La Vista Conference Center La Vista, NE The 53 rd SEDC will feature a National Drilling Association (NDA) program, indoor exhibitors, outdoor displays, and a full agenda of technical presentations. We look forward to seeing you there! For more information contact: Or visit http://sedc.unl.edu/clinic/2018clinic.asp Local Planning Committee Matt Marxsen mmarxsen2@unl.edu (402) 472-6863 Registration Jacki Loomis jloomis3@unl.edu (402) 472-7550 46 FEBRUARY 2018 WorldWide Drilling Resource ® Frequently-Used Geological Terms Part 69 Glossary Adapted from the Dictionary of Geological Terms P Pore - A small to minute opening or interstice (pore)in a rock or soil. Also refers to a small opening in the wall or shell of an in- vertebrate animal. Pore Space - The open space on a rock or in soil, considered collectively. Porosimeter - An instrument used to determine the porosity of a rock sample by comparing the bulk volume of the sample with the aggregate volume of the pore spaces within it. Porosity - Usually stated as a percentage, this term refers to the ratio of the volume of the pores of a substance, as a rock or rock stratum, to the total volume of the mass. Porous - Containing voids, pores, or interstices, which may or may not interconnect. The term usually refers to smaller openings than those of a cellular rock. Porphyry - An igneous rock of any composition containing feldspar crystals embedded in a compact dark red or purple ground- mass. Portland Cement - A cement produced by the fine grinding of a carefully proportioned mixture of limestone and shale; heating the mixture to incipient fusion in a rotary kiln and fine grinding the resulting clinker. Developed in 1824 by Joseph Aspdin in England, the name is similar to Portland Stone, a widely used British building stone. Positive - Uniaxial crystals in which the extraordinary index of refraction is greater than the ordinary index and of biaxial crystals in which the intermediate index of refraction is closer in value to the lowest index, than to the highest. Positive Ore - An ore body which has been exposed and devel- oped on four sides, and for which tonnage and quality estimates have been made. Postmineral - In economic geology, this term is used to describe structural or other feature formed after mineralization. Potash - Potassium carbonate. A term loosely used for potas- sium oxide, potassium hydroxide, or even for potassium. Potash Feldspar - A misnomer for potassium feldspar. Potash Spar - An informal commercial term for potassium feldspar, or for a feldspar mixture. Look for more terms next month! Photo of potash by Joseph Gambogi U.S. Geological Survey.