Sulphur

Sulfur (in USA)
S

Jupiter's moon Io owes its colours to various forms of sulphur. A dark area near the crater Aristarchus on the moon may be a sulphur deposit.

The History Says

Sulphur was used by pagan priests 2,000 years before the birth of Christ. The Romans used sulphur or fumes from its combustion as an insecticide and to purify a sick room and cleanse its air of evil (Cunningham 1935). The same uses were reported by Homer in the Odyssey in 1000 B.C. Armed with the knowledge of gunpowder, Europeans demanded increasing quantities of sulphur, beginning in the 12th century.

The Present Scenario

Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, Epsom salts, and barite. It is recovered commercially from "salt domes" along the Gulf Coast of the USA.

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Sulfur, which is given a bad reputation because of its odor, can make a very beautiful mineral specimen, and fine quality examples are much sought after. The unmistakable deep yellow color is not matched by any other mineral and the nicely shaped crystal forms of sulfur add to its attractiveness. As for the odor, this occurs when water mixes with the sulfur and a small amount of hydrogen sulfide (H₂S) gas is produced. Although only small amounts of H₂S form from just moisture in the air, it is a powerful odor producer and is the dominating contributor to the odor of rotten eggs. Rest assured, though, that most specimens of sulfur, when kept dry, do not emit a strong odor and this is not difficult for collectors of fine sulfur specimens to ensure.

Although sulphur is in the same group in the periodic table as oxygen, there are more differences in the chemical characteristics of these elements than there are similarities. Thus, while oxygen always displays a valency of two, sulphur displays valences of four (in sulphur dioxide, SO₂), six (in thionyl chloride, socl₂) and eight (in sulphur hexafluoride, SF₈).

In the elemental state, sulphur exists in polymeric forms.

Sulphur is an essential element for living organisms, and is present in some amino-acids.

Hardness	Associated Minerals	Best Field Indicators	Streak	Colour	Varieties	Luster	Tenacity
1½ - 2½	Celestite Calcite Aragonite Gypsum	color, odor, heat sensitivity, lack of good cleavage and crystal habit.	Yellow	Lemon yellow	Selenian Sulphur	Resinous Greasy	Brittle

Found in following forms

Sulphide pyrite Marcasite (white pyrite)	FeS2
Pyrrhotite	FenSn+1
Cinnabar	Hgs
Galena	PbS
Sphalerite	ZnS
Chalcopyrite	CuFeS4
Chalcocite	Cu2S
Covellite	CuS
Bornite	Cu5FeS4
Sulphate	-
Gypsum	CaSO4.2H2O
Anhydrite	CaSO4
Barytes	BaSO4
Celestite	SrSO4

And other sulphide and sulphate minerals

Physical Characteristics

• Color is a strong yellow color in thick crystals and duller yellow in small crystals to pale yellow in massive or powdery forms. Can also be reddish or greenish yellow with impurities.
• Luster is vitreous to more often resinous or earthy in massive forms.
• Transparency is transparent to translucent.
• Crystal System is orthorhombic; 2/m 2/m 2/m
• Crystal Habits include mostly massive or powdery forms but well shaped blocky crystals are common. Crystals can be made up of two dipyramids, one with steeper faces than the other, prisms and/or pinacoids in various combinations.
• Cleavage is very poor in two directions.
• Fracture is conchoidal.
• Streak is yellow.
• Hardness is 2.
• Specific Gravity is 2.0 - 2.1 (well below average)
• Other Characteristics: odor (see above), poor heat conductivity makes it brittle when heated and can actually crack if held tightly in a person's hand.
• Best Field Indicators are color, odor, heat sensitivity, lack of good cleavage and crystal habit.

Treaty

In 1985, twenty-one countries (all European except Canada) signed the "Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution on the Reduction of Sulphur Emissions or their Transboundary Fluxes by at Least 30 Per Cent." It aims to reduce annual sulphur emissions -- the main cause of acid rain -- by at least 30 per cent in the year 1993. Since then, a new treaty is currently in the process of negotiation. The most important issue on the negotiating table is the inclusion of East European countries and the most effective method for inclusion. Should Western European sponsors of the original treaty assist its neighbors in acquiring expensive power scrubbers, provided by Western business? The balance between domestic business interests, Germany's $40 billion pollution-control industry, and international environmental interests are crucial factors guiding the negotiations.

Notable Occurrences

Michigan and Ohio, USA
Sicily
Poland
Chile

Sulphur deposition

The deposition of sulphur has decreased significantly over recent years and is predicted to decrease further by 2010. This reflects a 71% decrease in sulphur dioxide emissions from 1987 to 2001, which led to 74% less dry deposition and 44.5% less wet deposition. These reductions reflect investments in flue gas desulphurisation technology and alternative fuel sources at power stations. Reductions in emissions of transboundary air pollutants are agreed at International level.