WorldWide Drilling Resource

Frequently-Used Geological Terms Part 29 Glossary Adapted from the Dictionary of Geological Terms I - Continued Inclined Fold - A fold whose axial sur- face is inclined from the vertical and in which one limb may be steeper than the other. Inclinometer - An instrument used to measure inclination in a well bore. Also refers to an instrument used to meas- ure magnetic inclination. Inclusion - A fragment of older rock within an igneous rock which it may, or may not, be genetically related. Incretion - A cylindrical mass of miner- al matter with a hollow core found in a rock. Index Horizon - A structural surface used as a reference in analyzing the geologic structure of an area. Index Map - A map, usually of small scale, depicting the location of a small area in relation to, or within, a larger area; e.g. a map showing a mine property in relation to the main feature of the sur- rounding area. Index Mineral - A mineral formed under specific pressure and temperature con- ditions providing the metamorphic his- tory of the rock in which it is found. Indicated Ore - Ore with quantitative estimates of tonnage and grade, made partly from inference, and partly from specific sampling. Indicator - A geological feature or other feature suggesting the presence of a mineral. Indigenous - Originating from, or native to, a specific place. Induction Log - A continuous record of the conductivity of strata crossed by a borehole as a function of depth. Indurated - A rock or soil hardened or consolidated by pressure, cementation, or heat. Industrial Diamonds - General term for diamonds used in drilling and wire drawing, and as abrasives. Industrial Mineral - Any rock, mineral, or other naturally-occurring substance of Diagram courtesy of answers.com 33 WorldWide Drilling Resource ® APRIL 2014 economic value, excluding metallic ores, mineral fuels, and gemstones. Inferred Ore - Ore with quantitative estimates of tonnage and grade made only in a general way, based on geo- logic relationships and past mining rather than specific sampling. Infiltration - Flow of a fluid into a solid substance through pores or small open- ings; specifically the movement of water into soil or porous rock. Infiltration Rate - The rate at which soil can absorb falling rain or melting snow. Influent Stream - A stream, or reach of a stream, contributing water to the zone of saturation, and developing bank stor- age; its channel lies above the water table. More terms to come next month!