A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

I

Igneous rocks       Rocks formed by the solidification of molten material that originated within the Earth.

Ilmenite       An ore mineral of titanium, being an iron-titanium oxide.

Immediate roof       The roof strata immediately above the coalbed, requiring support during the excavation of coal.

Impregnated       Rocks or minerals saturated with some other substance.

In situ       In the natural or original position. Applied to a rock, soil, or fossil when occurring in the situation in which it was originally formed or deposited.

Inby       In the direction of the working face.

Incline       A rising slope.

Incline       Any entry to a mine that is not vertical (shaft) or horizontal (adit). Often incline is reserved for those entries that are too steep for a belt conveyor (+17 degrees -18 degrees), in which case a hoist and guide rails are employed. A belt conveyor incline is termed a slope. Alt: Secondary inclined opening, driven upward to connect levels, sometimes on the dip of a deposit; also called "inclined shaft".

Incompetent       Applied to strata, a formation, a rock, or a rock structure not combining sufficient firmness and flexibility to transmit a thrust and to lift a load by bending.

Incrustation       A coating or crust on a rock.

Indicated coal resources       Coal for which estimates of the rank, quality, and quantity have been computed partly from sample analyses and measurements and partly from reasonable geologic projections. The points of observation are ½ to 1 ½ miles apart. Indicated coal is projected to extend as an ½ mile wide belt that lies more than ¼ mile from the outcrop or points of observation or measurement.

Indicated value       The prehinluary value determined for a placer sample, before it is adjusted or corrected for known variables.

Induced polarization       A method of ground geophysical surveying employing an electrical current to determine indications of mineralization.

Industrial minerals       Non-metallic, non-fuel minerals used in their natural state in the chemical and manufacturing industries; they require some beneficiation. Examples: asbestos, gypsum, salt, graphite, mica, gravel, building stone and talc.

Inferred coal resources       Coal in unexplored extensions of the demonstrated resources for which estimates of the quality and size are based on geologic evidence and projection. Quantitative estimates are based largely on broad knowledge of the geologic character of the deposit and for which there are few, if any, samples or measurements. The estimates are based on an assumed continuity or repletion of which there is geologic evidence; this evidence may include comparison with deposits of similar type. Bodies that are completely concealed may be included if there is specific geologic evidence of their presence. The points of observation are 1 ½ to 6 miles apart.

Initial public offering       The first sale of shares to the public, usually by subscription from a group of investment dealers.

Institutional investors       Pension funds and mutual funds, managing money for a large number of individual investors.

Intake       The passage through which fresh air is drawn or forced into a mine or to a section of a mine.

Interbedded       Occurring between distinct rock layers or strata.

Intermediate rock       An igneous rock containing 52% to 66% quartz.