The Fuel of Hell

The Fuel of HellSulphur Mines near San Felipe
Written by GeoRock, not for publication elsewhere without permission.

When we think of sulphur, it is usually associated with a wrinkling of the nose and the image of rotting eggs. Perhaps worse, Hell?s fire and brimstone comes to mind, as sulphur is thought to be the fuel of Hell (a belief passed along through Christian mythology). In ancient times, however, the Greeks? name for sulphur meant divinity. The mineral was thought to be the embodiment of fire and related to lightening.

Americans spell it ?sulfur,? because the American Chemical Society deemed it to be so, but the rest of the world spells the name as ?sulphur.? Regardless of it?s spelling, the chemical symbol is universal--a single capital ?S.? Sulphur is not only a mineral; it is also an element such as gold, silver, or copper. Whereas most minerals are composed of several elements, sulphur is composed of only the element sulphur.

With research, I was able to discover the names of two sulphur mines south of San Felipe, Municipal de Mexicali, Baja California Norte, Mexico. They are the San Carlos and the Delicias Mines.

Most sulphur, including that near San Felipe, is formed by volcanic action. It often occurs at or near active or extinct volcano crater rims at fumaroles. Fumaroles are holes from which vapor rises. It is an interesting mineral, as it does not form from a liquid. Instead, it is a sublimate. That means crystals or a deposit that forms when a substance is sublimated. Still wondering what that means? Sublimation is when a solid substance is heated into vapor, which when cools condenses back to a solid form without ever passing through a liquid state. Solid to vapor to solid. Get it? The vapor rises from the fumaroles and solidifies into sulphur without ever cooling to a liquid state.

Sulphur is also found in meteorites and at hot springs. Our moon?s crater Aristarchus has a dark area near it that is believed to be a sulphur deposit. And Jupiter?s moon IO displays vibrant colors due to various forms of sulphur.

Sulphur is one of the easiest minerals to recognize in the field. It is usually yellow. Crystals can be a brilliant to dull yellow, and the crusty, powdery form can be a pale whitish-yellow. The mineral emits a mild odor similar to rotten eggs, which intensifies if heated. It may have a greasy feel. Impurities of clay, selenium, or volcanic mixtures may color it differently to slightly red, green, brown, or gray. An interesting distinguishing feature is caused by its very poor heat conductivity. If one holds a crystal specimen to their ear, holding in the hand tightly, body heat will cause the crystals to crack, which can be heard. The surface layers of the crystal expand from the hand?s heat, while the interior is unaffected.

Sulphur crystals are orthorhombic, with steep biphyramidal and tabular crystals being common. Sometimes the crystals will be hollow skeletons. Also occurring are small grains, wheat sheaves, and encrustations. Sulphur can also be massive, which means deposits that are non-crystals and often are earthy, or powdery. If not earthy, then massive deposits are uniformly indistinguishable crystals forming large masses. Often bubbly holes can be seen throughout the surface of the harder (but not powdery) massive specimens. When ?reniform? in shape, it looks like kidney shaped clusters. Sulphur can also form as stalactitic shape, in pendant columns such as stalactites or stalagmites. The luster is vitreous to resinous or earthy. Transparency ranges from transparent to translucent to opaque. Sulphur has very poor cleavage in two directions, resulting in conchoidal fracturing (such as the way obsidian breaks appear). When rubbed on a non-glazed piece of porcelain, also known as a ?streak plate,? it produces a yellow streak. It is non-florescent.

In mineralogy, all minerals have a hardness rating according to Moh?s Relative Hardness Scale. Given a smooth surface of a mineral, its resistance to scratching can be rated. Moh?s scale goes from one to ten, listing ten minerals to which other minerals scratching resistance can be compared. Talc (you know the stuff, baby powder?) is number one. It is so soft that just the pressure of fingers can break it apart. Gypsum, number 2, can be scratched easily with your fingernail. Number ten is a woman?s best friend, the diamond. Sulphur, depending on whether it is earthy or crystalline, has a hardness of 1.5 to 2.5.

Given the softness and brittleness of sulphur, it should be obvious that specimens should be handled with care. When collecting, do not recklessly hammer away destroying samples that others could collect in the future. Once a fine specimen is procured, wrap it in toilet paper for protection. At home, do not wash it, do not store it wet or in humid conditions. Keep specimens away from heat and sunlight to avoid cracking the crystals. The crystals are very brittle and should be handled carefully. They should especially be kept dry!

Other minerals that are commonly found with sulphur include realgar, cinnabar, barite, celestite, calcite, ******ite, gypsum, and anhydrite. Which minerals can be found with the sulphur depends on the method in which the sulphur formed. In the attached photo, the orangish-red mineral seen is realgar, an arsenic sulfide (capital A, small s, capital S, spelled out because web program changes it to "fanny"). Realgar leans more to being the mineral orpiment (As2S3) when it is bright orange in color. Realgar is more reddish. These two minerals can usually be found together. They differ in that orpiment has 2 atoms of arsenic and 3 atoms of sulphur, whereas realgar only has one of each element atom. The opaque white powdery looking base mineral that the sulphur crystals can be found on is called gypsum (CaSO4.2H2O).

The gypsum is earthy, with a slight pearly luster and a hardness of 1.5-2, with some specimens having a slightly noticeable fiberous quality. The color is opaque white.

A few specimens had some massive (non-crystalline) galena. The silvery-metallic mineral is composed of one atom of lead and one atom of sulphur (PbS). Also found were some embedded colorless ******ite crystals (CaCO3), about 0.5 cm in length. One specimen had about 4 rhombohedron calcite crystals.

At the San Felipe mines, sulphur was found in the form of earthy massive; massive crystalline intrusions; and grade B glassy, rounded sulfur crystals. A few more distinct crystals were discovered in non-weathered areas.

Commercially sulphur is mined in a method known as the Frasch process. Along the gulf coast of the United States at the salt domes, underground sulphur deposits are forced to the surface. Hot water and steam, at a temperature of 160 degrees Celsius and compressed air (25 atmospheres), is shot down the mines. The sulphur melts into brine, which is pumped to the surface where it is allowed to cool in large basins. The water evaporates leaving sulphur as pure as 99.5%. Sadly, this process destroys all sulphur specimens.

Sulphur is used as a preservative in wines; a bleaching agent for dried fruits such as apricots; in the production of black powder, matches, explosives and batteries; to create rubber, dyes, insecticide, fungicide, and phosphatic fertilizers. A tremendous amount is used in the production of sulfuric acid. Even our bodies use sulphur as a major constituent of fats, body fluids, and in the formation of the skeleton.

So what causes that rotten egg smell? It happens when water (H2O) mixes with sulphur and produces hydrogen sulfide gas (H2S). Only small amounts of H2S is produced from the moisture in the air, but it is enough to smell sulphur?s distinct scent. If one wishes to play a practical joke, place a wet sulphur specimen under someone?s back car seat. Only do this to someone you don?t like, as even after the mineral has been removed the smell will linger for some time.

As for mi amigos, sulphur burns easily producing a blue flame as it becomes sulfur dioxide. Of course, the gas smells of brimstone. And we all know that Baja is one place that Hell isn?t, so let?s stick to the copper oxide ore for our magic rocks.


(I have a photo of several specimens, but have tried everything I know to no avail. I can't figure out how to post it here. Sorry.)



[Edited on 2-22-2004 by GeoRock]

Suzanne....

Good primer.

Great Post!

Thanks, Geo!