Sulpharsenites - Jamesonite,
Feather Ore Composition

The minerals in this division are considered to be salts of the sulpho-acids of trivalent arsenic, antimony and bismuth. Various types of these acids are found, such as H3AsS3, H2AsS2, H4As2S5, etc. a subdivision includes the sulpharsenates, etc. being chiefly salts of the acid H3AsS4. the metals observed are most commonly copper, silver and lead; also at times iron, zinc and mercury.

Jamesonite Feather Ore
Composition. Sulphantimonite of lead. There are apparently several different compounds that are of the designated as “feather ore .” A formula suggested for jamesonite is 4PbS. FeS. 3Sb2S3.

Crystallization. Orthorhombic.

Structure. Usually in acicular crystals or in capillary forms. Also fibrou to compact massive.

Physical Properties. Basal cleavage. Britle. H. = 2-3. G. = 5.5-6. Metallic luster. Color and streak steel-gray to grayish black.

Tests. Fusible at 1. on charcoal gives a combination coating of lead and antimony oxides. Roasted in O. T. gives sublimate of antimony oxides. Heated on charcoal with a mixture of potassium iodide and sulfur gives a chrome- yellow coating of lead iodide. Recognized by above test and characteristic fibrous structure. Difficult to distinguish from similar species (see below ).

Occurrence. Jamesonite is found in ore veins associated with other lead sulphosalts, with galena, stibnite, tetrahedritic, sphalerite, etc. found in Cornwall, England, and from various localities in Czechoslovakia, Rumania, Saxony, etc.; from Tasmania and Bolivia.Noted in the United States from States from Sevier County, Arkansas, and at Silver city, Pennington Co., South Dakota.

Similar Species. There are a number of minerals similar to jamesonite in composition and general physical characteristics whose relations to each other in many cases are not thoroughly understood. These include such minerals as zinkenite, PbS.Sb2S3; plagionite, 5PbS.4Sb2S3, senseyite, 5PbS.2Sb2S3; boulangerite, 5PbS.Sb2S3; meneghinite, 4PbS.Sb2S3; geocrinite, 5PbS.Sb2S3.