Mining Glossary

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

P

Panel - System of coal extraction in which the ground is laid off in separate districts or panels, pillars of extra size being left between.

Parting - A natural, usually smooth, separation between strata.

Peat - There are two types of peat, low moor (Flachmoor) and high moor (Hochmoor) peat. Low moor peat is the most common starting material in coal genesis. It therefore constitutes a caustobiolith of low diagenetic degree. Peat is formed in marshes and swamps from the dead, and partly decomposed remains of the marsh vegetation. Stagnant ground water is necessary for peat formation to protect the residual plant material from decay. Peat has a yellowish brown to brownish black color, is generally of the fibrous consistency, and can be either plastic or friable; in its natural state it can be cut; further, it has a very high moisture content (above 75 percent, generally above 90 percent). It can be distinguished from brown coal by the fact that the greater part of its moisture content can be squeezed out by pressure (for example, in the hand). Peat also contains more plant material in a reasonably good state of preservation than brown coal.

Pillar - An area of coal or ore left to support the overlying strata or hanging-wall in a mine. Pillars are sometimes left permanently to support surface works or against old workings containing water. Coal pillars, such as those in pillar-and-stall mining, are extracted at a later period.

Pit - Any mine, quarry, or excavation area worked by the open-cut method to obtain material of value.

Pit Committee - A joint committee of employer and workers dealing with the labor problems of a mine.

Place - The part of a mine in which a miner works by contract is known as his "place" or "working place." A point at which the cutting of coal is being carried on.

Portal - Any entrance to a mine. The rock face at which tunnel driving is started. Also called point of attack. A nearly level opening into a tunnel. The surface entrance to a drift, tunnel, adit, or entry.

Portal to Portal - A term now frequently encountered in disputes over what constitutes compensable "working time" under Federal laws. Portal literally means "entrance" and, in underground coal mining, portal refers to mine mouth or entry at surface. Hence, portal-to-portal as a descriptive term means strictly elapsed time from entry through the portal to exit on return.

Post - A mine timber, or any upright timber, but more commonly used to refer to the uprights which support the roof cross-pieces. Commonly used in metal mines instead of leg which is the coal miner's term, especially in the Far West regions of the United States. The support fastened between the roof and floor of a coal seam used with certain types of mining machines or augers. A pillar of coal or ore.

Powdered Coal (Pulverized Coal) - Coal that has been crushed to a fine dust by grinding mills. The latter are often air swept, the velocity of the air being so regulated that particles of coal, when sufficiently reduced, are carried away. Pulverized coal particles of which about 99 percent are below 0.01 inch in diameter will burn very rapidly and efficiently. Low-grade coal may be pulverized and conveyed from the mill by air into the boiler plant.

Power Shovel - An excavating and loading machine consisting of a digging bucket at the end of an arm suspended from a boom, which extends crane-like from that part of the machine which houses the power plant. When digging the bucket moves forward and upward so that the machine does not usually excavate below the level at which it stands.

Pregnant Solution - A value-bearing solution in a hydrometallurgical operation.

Preparation Plant - Strictly speaking, a preparation plant may be any facility where coal is prepared for market, but by common usage it has come to mean a rather elaborate collection of facilities where coal is separated from its impurities, washed and sized, and loaded for shipment.

Proximate Analysis - The determination of the compounds contained in a mixture as distinguished from ultimate analysis, which is the determination of the elements contained in a compound. Used in the analysis of scoal.