Marcasite and Pyrite

ID	248
Mineral	Marcasite Pyrite
Location	Ilsfeld - Baden-Württemberg - Germany
Fluorescence	LW-UV: close SW-UV: close
Mindat.org	View Marcasite information at mindat.org View Pyrite information at mindat.org

Mindat data

ID	2571
Long ID	1:1:2571:9
Formula	`FeS₂`
IMA Status	0 1
Other Occurrences	Most frequently found in sedimentary rocks and coal beds, as a replacement mineral forming fossils, it is a mineral of low-temperature, near-surface, environments, forming from acid solutions. Pyrite, the more stable form of FeS^2, forms under conditions of higher temperatures and lower acidity or alkaline environments.
Discovery Year	1845
Diapheny	Opaque
Cleavage	Distinct on {101}. {110} in traces.
Tenacity	brittle
Colour	Pale brass-yellow, tin-white on fresh exposures.
Hardness (min)	6.0
Hardness (max)	6.5
Lustre	Metallic
About the name	Early use of the word marcasite seems to have been unspecific. The word is Arabic or Moorish and was applied to pyrite and similar metallic bronze colored minerals. Walter Pope (1665) mentioned marcasite occurring in the mercury ores of the Idria Mine, Cividale del Friuli in the Julian Alps of Slovenia: "There are also several Marcasites and stones, which seem to have specks of Gold in them, but upon trial they say, they find none in them. These round stones are some of them very ponderous, and well impregnated with Mercury; others light, having little or none in them." The mercury ore at Idria does contain metallic golden specks of what is now called marcasite, but it also has metallic golden pyrite. Johnathan Hill used the name marcasite in 1771, but his usage was also indiscriminate and was a term for any massive "pyrites" or "mundic". In 1845, Wilhelm Karl von Haidinger defined marcasite as the mineral is known today.
Streak	Dark-gray to black.
Crystal System	Orthorhombic
Cleavage Type	Distinct/Good
Fracture type	Conchoidal,Sub-Conchoidal
Morphology	Crystals usually tabular on {010}, also pyramidal, faces often curved, frequently twinned; also stalactic, globular, or reniform with radiating internal structure.
Twinning	Common on {101}, forming "swallowtail" contact twins; this may be repeated to form stellate fivelings. Less common on {011}.
UV	Not fluorescent in ultraviolet light
Comment Luster	Frequently iridescence obscures the luster and color
shortcode_ima	Mrc
Group	Marcasite Group

ID	3314
Long ID	1:1:3314:1
Formula	`FeS₂`
IMA Status	0 1
Other Occurrences	Common in many rock types, igneous, metamorphic and sedimentary.
Diapheny	Opaque
Cleavage	Indistinct on {001}.
Tenacity	brittle
Colour	Pale brass-yellow
Hardness (min)	6.0
Hardness (max)	6.5
About the name	Named in antiquity from the Greek "pyr" for "fire", because sparks flew from it when struck with another mineral or metal. Known to Dioscorides (~50 CE) under the name "περι υληζ ιατρικηζ" which included both pyrite and chalcopyrite.
Streak	Greenish-black
Crystal System	Isometric
Cleavage Type	Poor/Indistinct
Fracture type	Irregular/Uneven,Conchoidal
Morphology	Typically cubic or pyritohedral (pentagonal dodecahedral), sometimes octahedral and combinations are common, resulting in striated faces. Less frequently octahedral, most commonly massive, granular, and sometimes radiating, reniform, discoidal or globular.
Twinning	On [110], interpenetrating ('Iron Cross Law'). Twin axis [001] and twin plane {011}, penetration and contact twins. Twinning on (111) was described by Nicol (1904), Goldschmidt and Nicol (1904) and Gaubert (1928), all of whom considered it rare.
UV	Not fluorescent in UV
Thermal Behaviour	Heated in a closed tube gives a sublimate of sulfur and a magnetic residue.
shortcode_ima	Py
Group	Pyrite Group

Price: € 25

Dimensions: Not registered

Weight: 93 g

Visibile in overview:

Update mindat:

Notes:

Symbol	Element
Fe	Iron
S	Sulfur

Marcasite and Pyrite

Mindat data

Details