- Industry: Mining
- Number of terms: 33118
- Number of blossaries: 0
- Company Profile:
The U.S. Bureau of Mines (USBM) was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.
Founded on May 16, 1910, through the Organic Act (Public Law 179), USBM's missions ...
A pillar method of working a relatively thick coal seam by a system of compartments; a modification of pillar-and-stall.
Industry:Mining
A pillar method of working in which the coal pillars are not extracted until the whole workings have been driven to the boundary. It is sometimes adopted when a seam a short distance above is worked simultaneously. Delayed pillar working increases the difficulty of ventilation, and the amount of deadwork is increased because of the crushing of coal pillars.
Industry:Mining
A pillar method of working often adopted in extracting a proportion of thick deposits of salt or gypsum. The method may be adopted where the value of the mineral in the pillars is less than the cost of setting artificial supports.
Industry:Mining
A pillar method of working suitable for seams 4 ft (1.2 m) and over in thickness. Three or more narrow headings are driven rapidly with machines at about 30-yd (10-m) centers with crosscuts for ventilation. The headings are 10 ft (3 m) or more wide and 5 to 6 ft (approx. 2 m) high or seam thickness. Upon reaching the boundary, the pillars formed by the headings are extracted, again with machines, on the retreat. This method is favored in the United States and the heading work is quite as productive, if not more so, than pillar working.
Industry:Mining
A pilot in the surface of which no cutting points, such as diamonds or slugs, are inset.
Industry:Mining
A pilot-type noncoring bit having a pilot section that is an integral, nonreplaceable part of the bit.
Industry:Mining
A pinacoid of two parallel faces that intersect only the c crystallographic axis.
Industry:Mining
