Galena
- Galena (also hexahedral galena )
- Lead (II ) sulfide
Galena, also known by its mining designation galena, is a common mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the cubic crystal system with the composition of PbS is thus seen chemically lead (II ) sulfide.
Galena often developed crystals of perfect cube shape, but also octahedral, rare tabular or skeletal crystals and massive aggregates of lead- gray color and stroke color. Show Galenitkristalle, especially on fresh fracture surfaces, a strong metallic luster. Mineral aggregates, however, are usually dull. Occasionally Galenas occur with colorful tarnish.
Galena is by far the most important ore for the recovery of lead and because of the often additionally contained admixture of silver also an important silver ore.
Special Features
Usually galena is of light to dark, lead- gray color. On polished surfaces, however, it shows a pure white reflection color, serving as a color Normal in ore microscopy.
With a Mohs hardness of 2.5 to 3 galena still belongs to the soft minerals which, although no longer as the softer mineral gypsum ( 2) with a fingernail, but lighter than calcite ( 3) can be scratched with a copper coin.
Typical properties of galena in addition to its characteristic of many sulfide minerals metallic luster and the low hardness nor the very perfect cleavage on the face of the cube { 100} (rarely, even after the octahedral {111 }) and its high - the highest in comparison to the other lead ores - Density of 7.58 g / cm ³. Only the very rare occurrence of lead amalgam has with 11.96 g / cm ³ a higher density.
Before the blowpipe galena melts crackling forms on coal a greenish yellow coat and leaves after volatilization of sulfur a lead particle. In nitric acid ( HNO3) is decomposed galena, sulfur being deposited, and a white precipitate of lead sulfate ( PbSO4 ) forms.
Etymology and history
The Latin name " Galena " is handed down already by the Roman scholar Pliny the Elder (c. 23-79 AD). The use of the mining word "shine" for the lead ore is attested since the 16th century, but later became a general collective term for all the shiny metallic, sulfidic ores (copper gloss, silver gloss). Abraham Gottlob Werner (1749-1817) coined to distinguish the term " galena ", next came about in 1850, the term " galena " on.
Galena is one of the oldest ore minerals of cultural history for recovering lead. The previously oldest known lead finds date from the Stone Age settlement of Çatalhöyük ( Catal Huyuk ), eg of the period 5500-4800 BC. On a similar age is one in Yarim Tepe found in present-day Iraq Lead Ring appreciated. Among the most ancient peoples who produced or used lead, included the Babylonians, Egyptians and Romans. (see also Lead # History ).
In Ancient Greece, lead had already known. The Pb -Ag deposits of Laurion served but mainly for the production of silver, while the by-product of lead was usually discarded.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the galena belonged to the mineral class of " sulfides and sulfosalts " and then to the Department of " sulfides with the molar ratio of metal: sulfur, selenium, tellurium ≈ 1: 1" where as he named the " galena - series" with the system no. II/C.15 and the other members Alabandin, Altait, Clausthalite, Crerarit, Keilit, Niningerit and oldhamite formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz 's Mineral classification assigns the galena also in the department of " metal sulfides ( with the molar ratio ) M: S = 1: 1 ( and similar ) " a. However, this is further subdivided according to the dominant metal ions in the compound, so that the mineral according to its composition in the subdivision " with tin ( Sn ), lead ( Pb ), mercury (Hg ), etc. " is to find where it also eponymous the " Galenitgruppe " with the system number. 2.CD.10 and the other members Alabandin, Altait, Clausthalite, Keilit, Niningerit and oldhamite forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the galena in the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." He is also named as the " Galena Group ( isometric: Fm3m ) " with the system no. 02.08.01 and the other members Clausthalite, Altait, Alabandin, oldhamite, Niningerit, Borovskit, Crerarit and Keilit within the sub-division of " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n): p = 1: 1 to find. "
Varieties and modifications
Galena has in pure form a mass fraction of 86.6 % lead and 13.4% sulfur, which is only achieved with synthetically produced lead sulphide. Naturally arising galena always contains admixtures of other elements that replace either small amounts of lead or sulfur diadoch. From these simple chemical varieties are especially those with additions of silver, gold, bismuth and / or selenium known. Most varieties do not receive such proper names or provided only with the addition of the element contained ( eg " silver- galena " or " silver - galena "). "Uranium - galena " (aka " U- galena " ), however, contains the lead isotope 206Pb, which is formed from the decay of uranium isotope 238U. A further variety, in which a part of the sulfur is replaced by selenium is referred to as " Selenbleierz ". As another, most contained only in trace amounts, additives may include, but not of copper (Cu ), iron ( Fe), antimony (Sb ), zinc (Zn ), and arsenic (As ), and cadmium (Cd), tin (Sn ) and carbon (C ) draw near and are mostly due to fine adhesions or segregation of other mineral phases.
" Steinmannit " was initially mistaken for a different mineral and 1833 described by Franz Xaver Zippe as a new mineral from the lead mines at Pribram (Czech Republic), which consisted of leaden-gray, racemose to kidney-shaped aggregates with small and clear octahedral trained, ride-on crystals of the same mineral. Striking appeared Zippe especially in contrast to galena only weakly present cleavage. In addition, the mineral had a lower density ( 6.833 g / cm ³). However, the other properties ( crystal system, color, streak color, Mohs hardness ) resembled the galena. Zippe was as a composition of lead, antimony, and sulfur in the form of lead sulfur ( galena ) and antimony sulfur ( stibnite, stibnite ) in the approximate ratio of 3: 1 and a low proportion of silver to but could not make any more detailed analysis due to lack of equipment. He named the new minerals by the professor of chemistry at the Polytechnic Institute in Prague Johann Joseph Steinmann ( 1779-1833 ). In subsequent Mineralogical Tables Steinmannit is no longer regarded as a separate mineral species, but as a variety of galena. Thus leads among other things Sigmund Caspar Fischer in his "Handbook of Mineralogy " of 1840 besides various Formvarietäten also a so-called Steinmannit (also octahedral galena ) from Pribram in Bohemia and Paul Heinrich von Groth holds 1898 in his " Tabular overview of minerals according to their krystallographisch - chemical relationships sorted "in his note on galena ( galena ) found that Steinmannit is an antimony- and arsenic-containing galena. Kenngott (1818-1897), Reuss (1761-1830) and Black looked the other hand Steinmannit as impure mixture of galena, zinc sulphide ( sphalerite ) and sulphide of arsenic ( realgar ).
"Lead tail " are strongly plastically deformed by tectonic processes, rolled-out and fine -grained to coarse galena aggregates called. A special lead tail with high silver content and correspondingly lighter color was known by fishermen as " Weißgiltigerz ". According to other sources are the Weißgiltigerze (also Weißgültigerz or Weißgülden ) no longer a common name for gray silver ores, which were created at the analog Rotgültigerzen and as these are divided into dark and bright Weißgültigerze.
" Bleimulm " even queasy galena or lead blackness, is a scaly variety with little internal cohesion (slightly friable ), which was regarded by fishermen as destruction product.
" Knottenerz " (also Knotenerz or lead Sanderz ) is an intimate intergrowth of sandstone, galena and other lead ores that was found among others at Bleiberg in the Eifel.
"Knitting aperture" (also knitted galena ) is a like " knit " looking intergrown with silver sheen.
As " Quiroguit " is referred to by Groth a mixture of galena, stibnite and pyrite with very distorted crystals and as " Cuproplumbit " (also copper galena ) a mixture of PbS ( galena ) and Cu2S ( chalcocite ) with a predominant Galenitanteil. Also occurring in coarse aggregates minerals " Fournetit ", " Huascolith " and " Plumbomanganit " he considers mixture of galena with other ores.
Another, called " Schalenblende " known, mixture consists of sphalerite and wurtzite as well as additions of Galena and other lead sulphides.
As " Blaubleierz " (English Plumbeine ) is called a pseudomorph of galena after pyromorphite. In addition, however, other pseudomorphs such as after Cerussite are known.
Education and Locations
Galena is a so-called " completers - mineral ", which forms in intra- magmatic to cold thermal reservoirs. Even under sedimentary and metamorphic conditions of formation galena is stable. The vast majority of deposits are hydrothermal nature, where the mineral either in corridors of plutonic rocks ( rare volcanics ) crystallizes or is caused by displacement of other minerals, among others, in limestone and dolomite.
Often found in galena with sphalerite and chalcopyrite paragenesis. However, it can be associated according to its educational opportunities with many other minerals, such as, among others, barite, calcite, dolomite, marcasite, pyrite, siderite, tetrahedrite and quartz. Weathering in the oxidation zone of lead deposits of galena gradually goes into the minerals cerussite ( Weißbleierz ), anglesite ( Bleivitriol ), pyromorphite ( green or Braunbleierz ) Mimetite ( Arsenikbleispath ) and other secondary lead minerals over.
As a widespread mineral formation galena could be detected in many places around the world, where so far (as of 2013) are approximately 21,000 localities known as. Among the seven major producing nations for lead ore were 2011, the People's Republic of China ( 2.36 million tons ), Australia ( 621,000 tons ), the USA ( 342,000 tons ), Peru ( 230,000 tonnes ) and Mexico ( 223 717 tons ), Russia ( 113,000 tons ) and Bolivia ( 100 051 ).
Known due to exceptional Galenitfunde include Joplin and Ellington ( Sweetwater Mine) in Missouri, Galena, Kansas and Picher, Oklahoma in the United States, where Galenitkristalle of several dozen centimeters in diameter were revealed. Skeleton -shaped crystals and twins after the spinel law with a diameter of up to 20 cm were found in the " Nikolaevskiy Mine" ( Nikolai Mine ) at Dalnegorsk in Russia. Skeleton -shaped Galenitkristalle that are similar to those seen from synthetically produced bismuth, we know from burning coal dumps include the legendary " Pit Kateřina " at Radvanice v Čechách in the Czech Republic. One of the largest known Galenitkristalle with cubic habit, an edge length of 25 cm and a weight of 118 kg is kept at the British Museum in London. He was unearthed in the "Great Laxey Mine" on the Isle of Man.
Large Fund areas in Germany are or were, among others, the Freiberg transition district in the Saxon Erzgebirge with an area of 40 × 50 km, the hydrothermal veins in Clausthal- Zellerfeld, Bad Grund and Saint Andreas mountain in the Upper Harz and Neudorf in the eastern Harz; the synsedimentary - exhalativ - submarine ore deposits in the Rammelsberg near Goslar, the Triassic sediments in Mechernich and Untermaubach in North Rhine -Westphalia, as well as south of Heidelberg and Wiesloch Walhausen in Saarland.
In Austria galena occurred among others in the districts of Bad Bleiberg and Friesach Hut in Carinthia; in various mines in the industry, must and Waldviertel Lower Austria; in many places in the Hohe Tauern and the Habachtal in Salzburg; in several places in the Fischbacher Alps, in the district of Malmesbury and in the area around Bruck an der Mur in Styria; in the Inn Valley and in the Imst district - Nassereith in Tyrol; in some places in the district of Gmunden and the community Windischgarsten in the district of Kirchdorf an der Krems in Upper Austria as well as in some places in the Montafon Valley in Vorarlberg.
In Switzerland, you know the mineral so far mainly in the cantons of Bern ( Haslital ), Graubünden ( Albula valley, Val S- charl, Val Poschiavo), Ticino ( Malcantone ), Uri ( Reusstal ) and Wallis ( Binn Valley, Val d' Anniviers ).
Other localities lie include Afghanistan, Algeria, Angola, Antarctica, Argentina, Armenia, Azerbaijan, Belgium, Botswana, Brazil, Bulgaria, Chile, Ecuador, Finland, France, Ghana, Greece, Greenland, India, Indonesia, Iran, Ireland, Italy, Japan, Cambodia, Canada, Kazakhstan, Kyrgyzstan, Colombia, Madagascar, Morocco, Mongolia, Myanmar, Namibia, Netherlands, New Zealand, Norway, Papua New Guinea, the Philippines, Poland, Portugal, Romania, Saudi Arabia, Sweden, Slovakia, Spain, South Africa, Tunisia, Turkey, Venezuela, Vietnam, the United Kingdom ( England, Scotland, Wales).
Also in Mineral samples from the hydrothermal field of transatlantic geotraverse ( Trans-Atlantic geotraverse hydrothermal field, TAG) at the Mid-Atlantic Ridge and the Manus Basin of the Bismarck Sea and from several locations on the East Pacific Rise (EPR 9-10 ° N, Guaymas Basin, Juan- de Fuca ridge ) could be detected galena.
Morphology
The most common observed in galena crystal forms are the cube { 100}, { 110} the rhombic dodecahedron and the cuboctahedron as a combination of cube and octahedron {111 }. Only rarely, however, purely octahedral crystals and Trisoktaeder can be found { 221 }.
Furthermore, also the octahedral crystal twins with (111 ) as twin plane and epitaxial intergrowths such as with pyrite known.
Octahedral galena
Almost perfect cuboctahedron ( combination cube - octahedron )
Twin crystal, distorted tabular after the twin plane (111 )
Crystal structure
Galena crystallized isotypic with halite (NaCl ) in the cubic crystal system in the space group Fm3m ( Raumgruppen-Nr. 225 ) with the lattice parameters a = 5.92 Å and four formula units per unit cell.
The crystal structure of galena (PbS ) corresponds to the sodium chloride structure and therefore consists of two shifted by half a unit cell, face-centered cubic lattices reason of lead and sulfur atoms. In other words, each lead atom is octahedrally surrounded by six sulfur atoms (coordinated ) and vice versa, each sulfur atom of six lead atoms.
Other minerals of this structure type are Altait ( Bleitellurit, PbTe ), Clausthalite ( Bleiselenit, PbSe ) and Alabandin ( manganese sulfide, α - MnS ).
Use
The raw material
Galena is the most important lead ore due to its high lead content of up to 87 %, and its widespread use. Although the resulting from it secondary minerals cerussite, pyromorphite, anglesite and Mimetite have a similarly high lead content, are in contrast to galena but much less common. Because of its frequent additions of silver, which can amount to several percent by weight, but on average only between 0.005 and 0.4 %, galena is also an important silver ore. The silver contained is removed after roasting and reduction using the Parkes process ( also Parkesieren ) from crude lead.
Due to its relatively simple extraction and its low melting point ( ≈ 327 ° C) lead was used early on to producing various commodities. We are especially famous lead vases of the Babylonians and lead pipes for water and sewage management and lead sheets for covering roofs and ship hulls by the Romans. The negative consequences, among other things due to the use of lead in wine vessels, which led to the formation of sugar of lead, and the wine made sweeter, were already known in antiquity and passed down through the Latin term " lead poisoning " for lead poisoning.
For the use of lead in modern times see Lead # use.
Other uses
As early as the Old Kingdom of Egypt the silver-gray galena was used in cosmetics, beside the green malachite mainly to accentuate the eyes. Heat treatment in the fire finely crushed galena ( red lead ) could also convert and use it as rouge for lips and cheeks in a reddish pigment. Distinguished Greek women brightened face and skin with white lead, that first had to be made of elemental lead.
Due to its property as a semiconductor galena or lead (II ) sulfide in the early radio technology in detector receivers as a rectifier ( demodulator ) used. In addition, the minerals used for the production of corrosion-resistant glazes for various ceramic products, as well as for the reduction of the Self- contained in the 19th century old matches white phosphorus.
Manipulation and imitation
The fact that it is not the galena to a rarely occurring mineral and also often beautiful crystal steps and they have their counterfeits are found only in a few cases. Known exceptions are fakes of partially weggelösten crystals, as these are very rare and therefore achieve maximum prices in the minerals trade. The distinction, of course, to partially weggelösten crystals is difficult and can be done in case of doubt only by an electron- microscopic study of the surfaces on machining marks or residue from grinding or polishing agents.