Pyrargyrite is a
sulfosaltSulfosalt minerals are those complex sulfide minerals with the general formula: AmBnSp; where A represents a metal such as copper, lead, silver, iron and rarely mercury, zinc, vanadium; B usually represents semi-metal such as arsenic, antimony, bismuth and rarely...
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
consisting of
silverSilver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
sulfantimonide, Ag
3SbS
3. Known also as dark red silver
oreAn ore is a type of rock that contains minerals such as gemstones or metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or...
or ruby silver, it is an important source of the metal.
It is closely allied to, and isomorphous with, the corresponding sulfarsenide known as
proustiteProustite is a sulfosalt mineral consisting of silver sulfarsenide, Ag3AsS3, known also as light red silver or ruby silver ore, and an important source of the metal. It is closely allied to the corresponding sulfantimonide, pyrargyrite, from which it was distinguished by the...
or light red silver ore. Ruby silver or red silver ore (German
Rotgiiltigerz) was mentioned by
Georg AgricolaGeorgius Agricola was a German scholar and scientist. Known as "the father of mineralogy", he was born at Glauchau in Saxony. His real name was Georg Pawer; Agricola is the Latinised version of his name, Pawer/ meaning farmer...
in 1546, but the two species so closely resemble one another that they were not completely distinguished until chemical analyses of both were made.
Both crystallize in the ditrigonal pyramidal (hemimorphic-hemihedral) class of the rhombohedral system, possessing the same degree of symmetry as
tourmalineTourmaline is a crystal silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classed as a semi-precious stone and the gem comes in a wide variety of colors...
.
Pyrargyrite is a
sulfosaltSulfosalt minerals are those complex sulfide minerals with the general formula: AmBnSp; where A represents a metal such as copper, lead, silver, iron and rarely mercury, zinc, vanadium; B usually represents semi-metal such as arsenic, antimony, bismuth and rarely...
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
consisting of
silverSilver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
sulfantimonide, Ag
3SbS
3. Known also as dark red silver
oreAn ore is a type of rock that contains minerals such as gemstones or metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or...
or ruby silver, it is an important source of the metal.
It is closely allied to, and isomorphous with, the corresponding sulfarsenide known as
proustiteProustite is a sulfosalt mineral consisting of silver sulfarsenide, Ag3AsS3, known also as light red silver or ruby silver ore, and an important source of the metal. It is closely allied to the corresponding sulfantimonide, pyrargyrite, from which it was distinguished by the...
or light red silver ore. Ruby silver or red silver ore (German
Rotgiiltigerz) was mentioned by
Georg AgricolaGeorgius Agricola was a German scholar and scientist. Known as "the father of mineralogy", he was born at Glauchau in Saxony. His real name was Georg Pawer; Agricola is the Latinised version of his name, Pawer/ meaning farmer...
in 1546, but the two species so closely resemble one another that they were not completely distinguished until chemical analyses of both were made.
Both crystallize in the ditrigonal pyramidal (hemimorphic-hemihedral) class of the rhombohedral system, possessing the same degree of symmetry as
tourmalineTourmaline is a crystal silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classed as a semi-precious stone and the gem comes in a wide variety of colors...
. Crystals are perfectly developed and are usually prismatic in habit; they are frequently attached at one end, the hemimorphic character being then evident by the fact that the oblique striations on the prism faces are directed towards one end only of the crystal.
TwinningCrystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals....
according to several laws is not uncommon. The hexagonal prisms of pyrargyrite are usually terminated by a low hexagonal pyramid or by a drusy basal plane.
The color of pyrargyrite is usually greyish-black and the lustre metallic-adamantine; large crystals are opaque, but small ones and thin splinters are deep ruby-red by transmitted light, hence the name, from the
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
pyr and
argyros, "fire-silver" in allusion to color and silver content, given by E. F. Glocker in 1831. The streak is purplish-red, thus differing markedly from the scarlet streak of proustite and affording a ready means of distinguishing the two minerals. The Mohs hardness is 2.75, and the specific gravity 5.85. The refractive indices (nω=3.084 nε=2.881) and birefringence (δ=0.203) are very high. There is no very distinct cleavage and the fracture is conchoidal. The mineral occurs in metalliferous veins with
calciteCalcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 470°C, and vaterite is even less stable....
, argentiferous
galenaGalena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
, native silver, native
arsenicArsenic is the chemical element that has the symbol As, atomic number 33 and atomic mass 74.92. Arsenic was first documented by Albertus Magnus in 1250. Arsenic is a notoriously poisonous metalloid with many allotropic forms, including a yellow and several black and grey forms...
, &c. The best crystallized specimens are from
Sankt AndreasbergSankt Andreasberg is a town and a municipality in the district of Goslar, in Lower Saxony, Germany. It is situated in the Harz, approximately 7 km west of Braunlage, and 20 km east of Osterode am Harz.- History :...
in the
HarzThe Harz is a mountain range in central Germany. It is the highest mountain chain in northern Germany occupying parts of the German states of Lower Saxony, Saxony-Anhalt and Thuringia. The name Harz derives from the Middle High German word Hardt or Hart...
,
Freiberg-Places:* Freiberg, Saxony, Germany* Freiberg , Saxony, Germany* Freiberg am Neckar, Ludwigsburg, Baden-Württemberg, Germany* Freiberg in Moravia, birthplace of Sigmund Freud, a German exonym for Příbor, Czech Republic...
in
SaxonyThe Free State of Saxony is a federal state of Germany, located in the southeastern part of present-day Germany. It is the tenth-largest German state in area and the sixth largest in population , of Germany's sixteen states.Long in the heart of German-speaking Europe, Saxony became one of the new...
, and
GuanajuatoGuanajuato is a state in the central highlands of Mexico. It is named after its capital city, Guanajuato, which comes from the local indigenous language, meaning “Hill of Frogs.” Las Ranas is a nickname for people from this state as frogs are their state animal...
in
MexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It is not uncommon in many silver mines in the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, but rarely as distinct crystals; and it has been found in some
CornishCornwall is a county of England in the United Kingdom, forming the tip of the south-western peninsula of Great Britain. It is bordered to the north and west by the Atlantic Ocean, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Taken with the...
mines.
Although the red silver ores afford a good example of isomorphism, they rarely form mixtures; pyrargyrite rarely contains as much as 3% of arsenic replacing
antimonyAntimony is a chemical element with the symbol Sb and atomic number 51. A metalloid, antimony has four allotropic forms. The stable form of antimony is a blue-white metalloid. Yellow and black antimony are unstable non-metals...
, and the same is true of antimony in proustite. Dimorphous with pyrargyrite and proustite respectively are the rare monoclinic species pyrostilpnite or fireblende (Ag
3SbS
3) and xanthoconite (Ag
3AsS
3): these four minerals thus form an isodimorphous group.