Sulphur

native element

cinnabar

Formula: S
Native element
Specific gravity: 2.0 to 2.1
Hardness: 2
Streak: White
Colour: Yellow, brownish yellow, greenish yellow

With a low melting point of 113 degrees C, sulphur burns readily in air, with a low blue flame, and gives off choking fumes of sulphur-dioxide - acrid odor (forms sulphurous and eventually sulphuric acid in air).
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Environments:

Sedimentary environments
Volcanic sublimates (common)

Most native sulphur is formed by reduction of sulphates, especially in salt domes, where it forms by the bacterial decomposition of calcium sulphate. It also often occurs at or near the crater rims of active or extinct volcanoes, derived from volcanic gases and associated with realgar and cinnabar. The volcanic gases may produce sulphur as a direct sublimation product or by the incomplete oxidation of hydrogen sulphide gas. In sedimentary rocks sulphur is most commonly associated with anhydrite, gypsum and limestone.

At the Ball Eye mine and quarry, Cromford, Derbyshire, England, UK, native sulphur has been reported with anglesite in oxidised galena (RES p74).

At Tsumeb, Namibia, sulphur has been found with schultenite, anglesite and galena (R&M 93.6.548).

At Cookes Peak mining district, Luna county, New Mexico, USA, sulphur is found in small cavities in oxidising galena (R&M 94.3.236).

Alteration

covellite and ferric sulphate to ferrous sulphate, copper sulphate and sulphur
CuS + Fe2(SO4)3 → 2FeSO4 + CuSO4 + S
Covellite may be oxidised by the strong oxidising agent ferric sulphate according to the above reaction to form sulphur (AMU/b3-3-7.htm).

Common impurities: Se,Te

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