Illustrated Mining Terms


Panel - A mining block that generally comprises one operating unit.  
Panic bar - A switch, in the shape of a bar, used to cut off power at the machine in case of an emergency.  
Parting - (1) A small joint in coal or rock; (2) a layer of rock in a coal seam; (3) a side track or turnout in a haulage road.

Percentage extraction - The proportion of a coal seam which is removed from the mine. The remainder may represent coal in pillars or coal which is too thin or inferior to mine or lost in mining. Shallow coal mines working under townships, reservoirs, etc., may extract 50%, or less, of the entire seam, the remainder being left as pillars to protect the surface. Under favorable conditions, longwall mining may extract from 80 to 95% of the entire seam. With pillar methods of working, the extraction ranges from 50 to 90% depending on local conditions.  
Percussion drill - A drill, usually air powered, that delivers its energy through a pounding or hammering action.

Permissible - That which is allowable or permitted. It is most widely applied to mine equipment and explosives of all kinds which are similar in all respects to samples that have passed certain tests of the MSHA and can be used with safety in accordance with specified conditions where hazards from explosive gas or coal dust exist.  
Permit – As it pertains to mining, a document issued by a regulatory agency that gives approval for mining operations to take place.  
Pillar - An area of coal left to support the overlying strata in a mine; sometimes left permanently to support surface structures.
Pillar robbing - The systematic removal of the pillars between rooms or chambers to regulate the subsidence of the roof. Also termed "bridging back" the pillar, "drawing" the pillar, or "pulling" the pillar.  
Pinch - A compression of the walls of a vein or the roof and floor of a orebodyso as to "squeeze" out the ore.  
Pinning - Roof bolting.   

Roof Bolting at the Festival

Pitch - The inclination of a seam; the rise of a seam.  
Placer - any deposit of minerals not in place, usually occurs in gravel

Plan - A map showing features such as mine workings or geological structures on a horizontal plane.

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Porosity - the void space in rock or soil, usually expressed as the ratio of the volume of voids to the total volume of the material.
Portal - The structure surrounding the immediate entrance to a mine; the mouth of an adit or tunnel.

Subway Portal

Post - The vertical member of a timber set.  
Powder - the miner's term for dynamite.  
Pressure - the force per unit area.

Primer (booster) - A package or cartridge of explosive which is designed specifically to transmit detonation to other explosives and which does not contain a detonator.  
Prop - Coal mining term for any single post used as roof support. Props may be timber or steel; if steel--screwed, yieldable, or hydraulic.  

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