Pyrite, often called "Fools Gold", has a silvery-yellow to golden metallic colour. It is very common and may occur in large crystals. It has been used by ancient civilisations as jewellery, but is hardly used nowadays. Pyrite is sometimes incorrectly known as Marcasite in the gemstone trade. Marcasite is mineral that is a polymorph of Pyrite, and can be fragile and unstable, and is not fit for gemstone use.
Occurrence of Marcasite
Marcasite and Pyrite
The mineral pyrite, or iron pyrite, also known as fool's gold, is an iron sulphide with the chemical components FeS2. This mineral's metallic luster and faded brass-yellow hue give it a superficial resemblance to gold, therefore the well-known nickname of idiot's gold. The color has additionally led to the nicknames brass, brazzle, and Brazil, typically used to refer to pyrite observed in coal.
Pyrite is the most not unusual of the sulphide minerals. The name pyrite is derived from the Greek (pyrit?S), "of fire" or "in hearth", in flip from (pyr), "fireplace". In ancient Roman times, this call became carried out to numerous forms of stone that would create sparks whilst struck in opposition to steel; Pliny the Elder described considered one of them as being brassy, nearly truely a connection with what we now call pyrite. By Georgius Agricola's time, c. 1550, the time period had grow to be a normal time period for all the sulphide minerals.
Pyrite is commonly discovered associated with other sulphides or oxides in quartz veins, sedimentary rock, and metamorphic rock, in addition to in coal beds and as a substitute mineral in fossils. Despite being nicknamed fool's gold, pyrite is once in a while found in affiliation with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite shape. In the Carlin?Kind gold deposits, arsenian pyrite contains up to zero.37 wt% gold.
Marcasite can be fashioned as each a number one or a secondary mineral. It generally paperwork under low-temperature especially acidic situations. It occurs in sedimentary rocks (shales, limestones and low grade coals) as well as in low temperature hydrothermal veins. Commonly associated minerals include pyrite, pyrrhotite, galena, sphalerite, fluorite, dolomite and calcite.
As a number one mineral it bureaucracy nodules, concretions and crystals in quite a few sedimentary rock, along with in the chalk layers observed on both sides of the English Channel at Dover, Kent, England and at Cap Blanc Nez, Pas De Calais, France, in which it paperwork as sharp man or woman crystals and crystal organizations, and nodules.
As a secondary mineral it paperwork by way of chemical alteration of a number one mineral along with pyrrhotite or chalcopyrite.
A mineral is described each by means of its chemical composition and its crystal structure. In some cases two special minerals have the equal chemical composition, however exceptional crystal structures. Known as polymorphs, these intriguing cases illustrate how the distinctive crystal structures can bring about quite distinctive physical properties.
Perhaps the maximum well-known case of a polymorph pair is diamond and graphite. Though both are composed absolutely of pure carbon, diamond has a cubic shape with robust bonds in 3 dimensions. Graphite, with the aid of assessment, bureaucracy in layers with only weak bonds among layers. As a result in their structural variations, diamond has a hardness of 10 on the Mohs scale, even as graphite fees only 1. Diamond is the ultimate abrasive, while graphite is a high-quality lubricant.
Another thrilling polymorph pair is marcasite and pyrite. Both minerals are composed of iron sulphide. But in which nobody should ever confuse diamond and graphite, it is able to be tough to inform pyrite and marcasite apart. In truth pyrite is frequently offered beneath the call marcasite inside the gemstone trade. But despite their apparent similarities, they have got some crucial differences, such that one can be used as a gem fabric even as the alternative cannot.
Pyrite has a cubic structure, steel luster and a yellow-gold shade that has earned it the nickname "idiot's gold". With a hardness of 6 to six.Five at the Mohs scale, pyrite is tough sufficient for use in jewellery. Pyrite is likewise tremendously dense, with a selected gravity of five.Zero to 5.2. Only hematite has a better density.
Marcasite tends to be lighter in color, and is now and again referred to as "white iron pyrite". Sometime marcasite has a greenish tint, or a multi-coloured tarnish this is the result of oxidation. But marcasite has an risky orthorhombic crystal shape and is at risk of fall apart and ruin apart. In some instances marcasite will react with moisture inside the air to supply sulphuric acid. For these motives marcasite is by no means used in jewellery. When a gemstone is bought as marcasite you can be pretty positive that it is really pyrite.
Blueite (S.H.Emmons): Nickel variety of marcasite, found in Denison Drury and Townships, Sudbury Dist., Ontario, Canada.
Lonchidite (August Breithaupt): Arsenic variety of marcasite, found at Churprinz Friedrich August Erbstolln Mine (Kurprinz Mine), Großschirma Freiberg, Erzgebirge, Saxony, Germany; ideal formula Fe(S, As)2.
Synonyms for this range:
- metalonchidite (Sandberger) described at Bernhard Mine near Hausach (Baden), Germany.
Sperkise designates a marcasite having twin spearhead crystal. Sperkise derives from the German Speerkies (Speer meaning spear and Kies gravel or stone). This twin is very common in the marcasite of a chalky origin, particularly those from the Cap Blanc Nez.
|Colour||Metallic, Yellow, Gray|
|Hardness||6 - 6.5|
|SG||4.9 - 5.2|