Sulfur
Authors: Jackie S., Thomas S., and Sam B.
Mineral Name: Sulfur
Chemical Composition: Sulfur has a chemical composition of 100% Sulfur (“S” on the periodic table) and a chemical formula of S8 (2)
Color: Bright Yellow to yellow-brown
Streak: Sulfur leaves a yellow or white streak.
Hardness: Sulfur is a 1.5-2.5 on Moh’s scale of hardness; it is very soft and can be scratched by a fingernail. (5)
Cleavage/Fracture: Sulfur minerals have conchoidal fracture. Conchoidal fracture is aa type of fracture that shows breakage that have smoothly curving surfaces. (7) This type of fracture is typically found in very fine grained minerals. It means that there are no planes of weakness found in the mineral.
Crystal Form: While most sulfur seen does not have clear crystal planes because it has been rubbed smooth by handling due to its softness, sulfur actually does form in crystal planes. (5) Generally the crystals are dipyramidal or tabular in shape; however, most specimens are massive in nature. (1)
Luster: Sulfur has an adamantine (diamond-like) luster when it is associated with large, well-formed crystals. Otherwise, fine-grained mineral samples look more resinous or dull. (5)
Special Features: Sulfur has a very distinct color. When burned, sulfur also puts out a very obvious smell, almost like that of a rotten egg.. This mineral often times is found to have a lot of small holes in it. (1)
Varieties: Sulfur doesn’t really have any other varieties, but it does have a polymorph called rosickyite. A polymorph is a mineral that has the same chemical composition but a different crystalline structure, like graphite and diamond. Rsickyite has all the same characteristics as sulfur but has a different crystal system.
Mineral Group: Sulfur fits into the group of Native Elements, meaning that it has a molecular structure of only one element (Sulfur). Other minerals that fall under this category are Copper and Diamond. (5)
Environment: Sulfur is usually associated with volcanic activity, both past or present activity. It can also form when transforming pyrite and other sulfide mineral deposits. Sulfur also forms by precipitation. (8) Sulfur can form in sedimentary evaporite environments deposits often as a product result of the breakdown of sulfates by bacteria. Sulfur can also form in hot springs and fumaroles through sublimation, meaning the change from gas directly to solid form. Also can be formed in igneous rocks, like basalt, during volcanic activity. (1)
Associated Rock types: Igneous rocks like basalt. Also evaporite sedimentary rocks like rock salt and gypsum rock.
Occurrence in North America: Instances of Sulfur deposits have been found throughout North America, the most numerous deposits being in Virginia State (155 deposits). (6)
Economic and Industrial Uses: Sulfur is a very important mineral, usually used as an industrial raw material. It is used in a lot of fertilizers and many industrial resources. (3) Sulfur is used to make sulphuric acid that fertilizer companies use in fertilizer. This helps increase crop yields in the field. Sulfuric Acid is processed in four steps. The first step is to actually extract the sulfur. The second step is to convert the sulfur into sulfur dioxide. The next step is to convert the sulfur dioxide to sulfur trioxide. The final step is to convert the sulfur trioxide to sulfuric acid. (9) The US is the second largest producer of sulfuric acid. Sulfur is also used in the wine industry to help sanitize equipment and stop any growth of bacteria in the wine or on equipment that interacts with wine. The gun industry also uses it in black gun powder.
First Notable Identification: It took centuries for scientists to identify sulfur as an element. Sulfur was often referred to as “brimstone” in the bible and as one of the two main elements. The other main element was mercury, named by ancient philosophers. (2)
How We Identified It: Similar to information in the special features, this mineral is usually very easily identify based on its color. It can also be identified by its lightweight and the brittle nature of the mineral. (1) When it is burned it creates a very distinct clear blue flame and has a very strong odor. (2)
Don’t Confuse It With: Talc which is also a very soft mineral. Talc and sulfur resemble the similar characteristics but sulfur is still yellow.
Bibliography:
“Minerals.net.” Sulfur: The mineral native Sulfur information and pictures, www.minerals.net/mineral/sulfur.aspx.
“SULFUR.” Chemistry Explained, www.chemistryexplained.com/elements/P-T/Sulfur.html.
“Learn More About Sulphur - Introduction.” The Sulphur Institute, www.sulphurinstitute.org/learnmore/sulphur101.cfm.
“Sulfur.” Geology, geology.com/minerals/sulfur.shtml. .
“Conchoidal fracture.” Sandatlas, www.sandatlas.org/conchoidal-fracture/.
University of Minnesota's Mineral Pages: Sulfur, www.esci.umn.edu/courses/1001/minerals/sulfur.shtml.
Lazonby, John. “Sulfuric acid.” The Essential Chemical Industry online, www.essentialchemicalindustry.org/chemicals/sulfuric-acid.html.