Fine grained and powdery, with a dull luster.

 

A powdery crust, created by evaporation.

 

Capable of being bent, then returning to original shape.

 

When a thin, crystalline crust forms on a rock due to evaporation and other causes.

 

Pattern of growth of a group of parallel crystals showing a set of faces arranged in a row.

 

An underground horizontal or near-horizontal passage used for haulage, ventilation, or as a mainway; a coal heading; a working place where the coal is extracted from the seam in the initial mining; same as "gate" and "roadway," both British terms.

 

Crystals growing on another crystals, in alignment with the crystal structure of the host crystal.

 

Angular or rounded crystals with three nearly equal perpendicular axis.

 

Wearing away and transformation of the earth's crust caused by water (rain, sea), ice and atmospheric agents (wind).

 

A crystal showing well-formed faces, generally complete.

 

In the broad sense, the whole range of mining activity from searching for and developing mineral deposits to developing the mine. In the strict sense, the search for mineral deposits up to discovery and includes the delineation of the deposit by means of drilling and sampling.

 

Any rapidly combustive or expanding substance. The energy released during this rapid combustion or expansion can be used to break rock.