Cinnabar – Millerite Group. Hexagonal, Cinnabar Composition

Cinnabar
Composition. Mercuric sulphide, HgS = Sulfur 13.8 mercury 86.2 Usually impure from admixture of clay, iron oxide, etc.

Crystallization. Hexagonal-rhombohedral; trapezohedral. Crystal usually rhombohedral, often in penetration twins. Trapezohedral rare.

Structure. Usually fine granular massive; also earthy and as incrustations. Crystals rare.

Physical Properties. H. = 2-2.5. G= 8.10. Adamantine luster when pure,. To dull and earthy when impure. Color vermilion-red when pure, to brownish-red when impure. Scarlet streak. Transparent to opaque.

Test. Wholly volatile when free from gangue. Gives black sublimate of mercury sulphide when heated alone in C.T. When carefully heated in T}C.T. with dry sodium carbonate gives globules of metallic mercury. Carefully roasted in O.T. gives odor of sulfur dioxide and sublimate of metallic mercury. Recognized usuallly by color, streak and hig specific gravity.

Occurrence. The most important ore of mercury, but found in quantity at comparatively few localities. Occurs filling fissures, cavities, etc., usually in sedimentary rocks; frequently as impregnations and replacemtns in sandstone or limestone. Associated with ppyrite, marcasite, sulfides of cooper, stibnite, realgar, gold, calcite, barite, quartz, fluorite, etc. (Always found in the neighborhood of igneous rock masses from which it is thought that the mercury was derived. Deposited probably through the agency ofr ascending hot water. The important localities for the occurrence of cinnabar are at Almaden, Spaiin; Idria in Gorizia; Italy; Huancavelica in southerm Peru; Provinces of Kweichow and Hunan, China; New Idria in San Benito Country, Napa Country, and New Almaden in Santa Clara Country, California; Terlingua, Brewster Country, Texas, Hepatic cinnabar in as inflammable variety with liver-brown color and sometimes a brownish streak, usually sourece granular or compact.

Name. The name cinnabar is supposed to have come from India, where it is applied to a red resin.

Use. The only important source of mercury.