a. Compact, fine-grained, lacking pore space. b. Rock or mineral with a high specific gravity.

Definition

acicular:

A brilliant luster like that of a diamond.

a. A mass of rock particles, grains of minerals, or both. b. Irregular mass of crystals. c. Sand, gravel, crushed stone or rock that forms the major part of concrete.

Containing sodium and/or potassium in excess of the amount needed to form feldspar with the available silica. An alkaline rock, for example, contains more than average amounts of potassium- and sodium-bearing minerals.

Without form; applied to rocks and minerals which have no definite external crystalline structure.

A mineral group that consists of common, dark-colored, rock-forming silicate minerals. The most common minerals are hornblende, tremolite, and actinolite.

A volcanic rock composed essentially of the mineral andesine and one or more of the mafic minerals.

Refers to a crystal with no well-formed external faces.