Note:  Do not rely on this information. It is very old.

Gangue

Gangue. This term is applied to the portion of the rock or earthy material which occurs mixed with metallic ores. The nature of the gangue hence varies with the nature of the rock surrounding the metalliferous lodes or veins, and may consist of felspar, fluorspar, granite, quartz, limestone, etc. The gangue is sometimes useful in the smelting of the metal, owing to its acting as a "flux," but a great quantity always detracts from the value of the ore. The terms veinstuff and matrix are also applied with the same signification.