GeoRock
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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Written by GeoRock, not for publication elsewhere without permission.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]
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David K
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Great details on my favorite Baja element. The sulfur mine we went to is called 'El Apache' on the topo map. The Delicias ejido owns it now.
The other Baja sulfur mine is closer to Mexicali and very easy (well, almost easy) to reach from Hwy. 5 near Rio Hardy. Here are photos of it: http://davidksbaja.com/baja_2001/page5.html
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GeoRock
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Pete and Alicia just read this report, or tried to, and said it was too technical. Hmmm, I suppose I should re-title it as "Everything you don't need
to know about Sulphur!" But for those who like more info than not, enjoy.
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Bedman
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Suzanne....
Maybe it's my personality type or maybe I just like the way you inform,"Straight to the point". Whichever, I like ALL the information you impart. I
remember reading your assay report on the Copper from L. A. Bay and enjoyed it fully. Keep up the Great reports.
Bedman
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Stephanie Jackter
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Good primer.
I have just gone from knowing not a thing about sulphur (which I at least, do know how to spell), to knowing a few things about sulphur. Thanks. -
Stephanie
When the goin' gets tough, the wierd turn pro
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Skeet/Loreto
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Geo. thank you for a very informative Report. Hope to see you again May 1st. Skeet/Loreto
"In God We Trust"
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Jack Swords
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Great Post!
Thank you for posting this information. This really enhances the Baja experience for everybody. Hope to read more posts from you relative to the
geology of Baja.
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Don Jorge
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Thanks Geo Roeck!
Great information for us wannabe rockhounds. I stopped at those sulfur mines circa 1972, collected some samples and haven't been back since. You
brought back some memories. Thanks!!
[Edited on 2-22-2004 by Don Jorge]
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bajalera
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Thanks, Geo!
En route from San Felipe to Calamajue in the '70s, my kids and I stopped at a little roadside mine that looked more like a rancher's cottage industry
than a commercial operation, and bought some really neat sulphur crystals. We've always been curious about the details, and you've supplied them.
bajalera
[Edited on 2-22-2004 by bajalera]
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David K
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Before the new road was built along the coast (1982), the road to Puertecitos passed through the sulfur mining valley.
Just north of the valley was the junction to Bahia Santa Maria (est. about 1970). At the junction were two roadside cafes (Lupe's and Tony's). The AAA
map even gave the name 'Junta Santa Maria' to the pair of cafes. I bet the mineral samples were an extra business for them.
The mine area was less than a mile away and no structure or people lived right there (it stinks too much).
After the new road was built and all traffic moved to it, Tony's and Lupe's disappeared.
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