pyrite

[Middle English perides, pirite, from Old French pirite, from Latin pyrītēs, flint. See pyrites.]

(foolz gold)

noun
Something that appears valuable but is worthless.

Etymology
Shakespeare wrote in The Merchant of Venice, "All that glisters is not gold." Fool's gold is another name for pyrite, also known as iron pyrite or iron sulfide. Its shiny yellow luster has many fooled into believing they have struck gold while holding a mineral of little value. The name pyrite is from Greek pyrites (of fire), from pyr (fire) because it produces sparks when struck against a hard surface. Some related words are fire, pyre, pyrosis (heartburn), pyromania (an irresistible impulse to set things on fire), and empyreal (relating to the sky or heaven, believed to contain pure light or fire)


Fool's gold:



[Photo: US Geological Survey]

For more information on pyrite, visit Britannica.com.

A gold-colored mineral that is often mistaken for real gold. Also known as Iron Pyrite.

Investopedia Says:
During historical periods of gold rushes, many less-than-knowledgeable miners would frequently believe that they hit the motherload upon finding a huge cache of fool's gold. Unfortunately, unlike the real stuff, fool's gold is relatively worthless.

Related Links:
To bamboozle someone out of their money is an age-old ruse. Learn about some of the gimmicks modern-day swindlers use and avoid becoming a statistic. Online Investment Scams Tutorial
Think the value of gold is unshakable? Read this chronicle of its rise and fall. The Gold Standard Revisited
Despite its historic and symbolic appeal, this metal is simply a commodity. Here we explore its meaning as an investment. What Is Wrong With Gold?

Environment

Ubiquitous; in all classes of rocks and all types of veins.

Often crystallized, most frequently in striated cubes, less commonly in octahedrons. Massive pyrite is common.

Light yellow. Luster metallic; hardness 6-6Ɖ; specific gravity 5.0; streak powdery greenish black; fracture conchoidal; cleavage none. Brittle.

Iron sulfide (46.6% Fe, 53.4% S).

Fuses easily, becoming magnetic and giving off sulfur dioxide (SO ₂ ) fumes. Insoluble in hydrochloric acid, but a fine powder will dissolve in concentrated nitric acid (HNO ₃ ).

The tarnished sulfide might be confused with chalcopyrite, but its great hardness is distinctive. It is slightly yellower and more slowly soluble in nitric acid than marcasite, giving a clear solution. It is harder than gold, and very brittle.

Any weathered rock formation that appears rust-stained probably contains--or contained--pyrite, a frequent associate of all sorts of metal ores. In addition, it forms concretionary masses in sedimentary rocks, which then frequently alter to very compact limonite balls. Golden discs called "pyrite dollars" are found in an Illinois coal formation, and more spherical concretions with brown oxidized skins are common in clays, slates, and other metamorphic rocks. Daisylike golden crystal disks with coarse cubic "petal" rims were found during the Dallas-Fort Worth airport construction. So often mistaken for gold it is popularly known as "fool's gold." Fine specimens have been found throughout the world. Particularly notable in the past were the large well-formed crystals from Leadville, Colorado, and well-developed crystal groups from Park City, Utah. Misshapen octahedral crystals containing 0.2 percent arsenic were found at French Creek, Pennsylvania. "Cathedral" pyrite was a name given to the large cubes with Gothic arch growth patterns on their faces. Many-faced complex and perfect crystals come from Rio Marina on the island of Elba, Italy. Quiruvilca and Cerro de Pasco, both in Peru, now yield outstanding octahedral crystals and pyritohedral groups. Many Mexican occurrences have been reported. Highly modified crystals in fine clusters are typical of Oruro and Colavi, Bolivia. Falun, Sweden, yielded a pyrite rich in cobalt. Fantastic groups of sharp cubes are broken from a limestone in Spain and reconstructed into startling staircases with cubes of up to 5 cm or more.

Pyrite was once important as a source of sulfur for the manufacture of sulfuric acid, and could be again. Invisible specks of gold between the grains frequently provide value to seemingly worthless but cyanide-leachable deposits, so it may be an important ore of gold.