Langite
Encyclopedia
Langite is a rare hydrated copper sulfate mineral
, with hydroxyl, found almost exclusively in druses
of small crystals. It is formed from the oxidation of copper sulfides
, and was first described in specimens from Cornwall
, England. It is dimorphous
with wroewolfeite. Langite was discovered in 1864 and named after the physicist and crystallographer Viktor von Lang
(1838-1921), who was Professor of Physics at the University of Vienna
, Austria.
. The crystal is built up of identical unit cells
stacked together, with no space in between. The unit cell for the monoclinic systen has a base which is a rhombus
, with sides a and c inclined at angle β. The third side b is perpendicular to both a and c. For langite the angle β is very close to 90°, so the unit cell is almost brick-shaped (as for the orthorhombic system). Different sources give slightly different values for the unit cell parameters, but they all fall within the ranges a = 7.118 Å to 7.137 Å, b = 6.031 Å to 6.034 Å, c = 11.209 Å to 11.217 Å, β = 90.00 to 90.02°, Z (the number of formula units per unit cell) = 2.
and a blue-green streak
. It has perfect cleavage
perpendicular to the c crystal axis, and distinct cleavage perpendicular to b. Twinning
is common, and typically repeated to give snowflake or star shaped groupings. The mineral is soft, with hardness
2.5 to 3, a little less than that of calcite. Fracture
is uneven, and specific gravity
is in the range 3.28 to 3.50, a little less than that of diamond.
The mineral is pleochroic
, with X light yellowish green, Y blue-green and Z sky blue.
, chalcophyllite
, connellite
, brochantite
, malachite
and gypsum
.
for langite, Fowey Consols, Tywardreath
, Par Area, St Austell
District, and St Just
, St Just District, both in Cornwall, England. The type material is conserved at the Natural History Museum
, Vienna, Austria, reference A.a.4353.
Other reported occurrences include:
Sulfate mineral
The sulfate minerals are a class of minerals which include the sulfate ion within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary minerals in the oxidizing zone of sulfide mineral deposits...
, with hydroxyl, found almost exclusively in druses
Druse (geology)
In geological usage druse or druzy is a coating of fine crystals on a rock fracture surface, vein or within a vug or geode.- Occurrence :Druse occurs worldwide, the most common is perhaps quartz druse within voids in chert or agates...
of small crystals. It is formed from the oxidation of copper sulfides
Copper sulfide
Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores....
, and was first described in specimens from Cornwall
Cornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
, England. It is dimorphous
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
with wroewolfeite. Langite was discovered in 1864 and named after the physicist and crystallographer Viktor von Lang
Viktor von Lang
Viktor von Lang was an Austrian chemist. He is counted among the pioneers and founders of crystal physics.-References:...
(1838-1921), who was Professor of Physics at the University of Vienna
University of Vienna
The University of Vienna is a public university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world...
, Austria.
Unit cell
Langite belongs to the monoclinic crystal class m, meaning that it has just one mirror plane, and no axes of rotational symmetryRotational symmetry
Generally speaking, an object with rotational symmetry is an object that looks the same after a certain amount of rotation. An object may have more than one rotational symmetry; for instance, if reflections or turning it over are not counted, the triskelion appearing on the Isle of Man's flag has...
. The crystal is built up of identical unit cells
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
stacked together, with no space in between. The unit cell for the monoclinic systen has a base which is a rhombus
Rhombus
In Euclidean geometry, a rhombus or rhomb is a convex quadrilateral whose four sides all have the same length. The rhombus is often called a diamond, after the diamonds suit in playing cards, or a lozenge, though the latter sometimes refers specifically to a rhombus with a 45° angle.Every...
, with sides a and c inclined at angle β. The third side b is perpendicular to both a and c. For langite the angle β is very close to 90°, so the unit cell is almost brick-shaped (as for the orthorhombic system). Different sources give slightly different values for the unit cell parameters, but they all fall within the ranges a = 7.118 Å to 7.137 Å, b = 6.031 Å to 6.034 Å, c = 11.209 Å to 11.217 Å, β = 90.00 to 90.02°, Z (the number of formula units per unit cell) = 2.
Physical properties
Langite usually occurs as druses of small greenish-blue crystals which may be scaly or earthy. It is translucent, with a vitreous to silky lusterLustre (mineralogy)
Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....
and a blue-green streak
Streak (mineralogy)
The streak of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a more consistent characteristic color, and is thus...
. It has perfect cleavage
Cleavage (crystal)
Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the...
perpendicular to the c crystal axis, and distinct cleavage perpendicular to b. Twinning
Crystal twinning
Crystal 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....
is common, and typically repeated to give snowflake or star shaped groupings. The mineral is soft, with hardness
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
2.5 to 3, a little less than that of calcite. Fracture
Fracture (mineralogy)
In the field of mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a mineral is fractured. Minerals often have a highly distinctive fracture, making it a principal feature used in their identification....
is uneven, and specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
is in the range 3.28 to 3.50, a little less than that of diamond.
Optical properties
Langite is biaxial (-). Since it is monoclinic, it has three different refractive indices, corresponding to the three crystallographic directions. All the refractive indices are in the range 1.64 to 1.80, which is comparatively large, almost as high as garnet. Different sources give these values:- Nx=1.641, Ny=1.690, Nz=1.712
- Nx=1.708, Ny=1.760, Nz=1.798
- Nx=1.641 to 1.654, Ny=1.690 to 1.713, Nz=1.705 to 1.722
- Nx=1.641, Ny=1.690, Nz=1.705 to 1.712
The mineral is pleochroic
Pleochroism
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles with polarized light.- Background :Anisotropic crystals will have optical properties that vary with the direction of light...
, with X light yellowish green, Y blue-green and Z sky blue.
Environment
Langite is an uncommon but widespread secondary mineral in the oxidised zone of copper sulfide deposits, which may be of post-mine formation. It is associated with wroewolfeite, posnjakite, serpierite, devillineDevilline
Devilline is a sulfate mineral with the chemical formula CaCu426•3H2O. The name originates from the French chemist's name, Henri Etienne Sainte-Claire Deville .Devilline crystallizes in the monoclinic system...
, chalcophyllite
Chalcophyllite
Chalcophyllite is a rare secondary copper arsenate mineral occurring in the oxidized zones of some arsenic-bearing copper deposits. It was first described from material collected in Germany...
, connellite
Connellite
Connellite is a very rare mineral species, a hydrous copper chloro-sulfate, Cu19[32|SO4|Cl4]·3H2O, crystallizing in the hexagonal system. It occurs as tufts of very delicate acicular crystals of a fine blue color, and is associated with other copper minerals of secondary origin, such as cuprite and...
, brochantite
Brochantite
Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is CuSO4·3Cu2. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it is named for its discoverer, the French geologist and mineralogist, A. J. M...
, malachite
Malachite
Malachite is a copper carbonate mineral, with the formula Cu2CO32. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms...
and gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
.
Occurrences
There are two type LocalitiesType locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
for langite, Fowey Consols, Tywardreath
Tywardreath
Tywardreath is a small hilltop village in southern Cornwall, United Kingdom. about north west of Fowey. It is located in a sheltered spot overlooking a silted up estuary opposite Par and near the beach of Par Sands...
, Par Area, St Austell
St Austell
St Austell is a civil parish and a major town in Cornwall, England, United Kingdom. It is situated on the south coast approximately ten miles south of Bodmin and 30 miles west of the border with Devon at Saltash...
District, and St Just
St Just in Penwith
St Just is a town and civil parish in Cornwall, England, United Kingdom. The parish encompasses the town of St Just and the nearby settlements of Trewellard, Pendeen and Kelynack: it is bounded by the parishes of Morvah to the north-east, Sancreed and Madron to the east, St Buryan and Sennen to...
, St Just District, both in Cornwall, England. The type material is conserved at the Natural History Museum
Naturhistorisches Museum
The Naturhistorisches Museum Wien or NHMW is a large museum located in Vienna, Austria.The collections displayed cover , and the museum has a website providing an overview as a video virtual tour....
, Vienna, Austria, reference A.a.4353.
Other reported occurrences include:
- With serpierite coating the bed of a water course affected by acid mine drainage at the Lloyd Copper Mine at Burraga, New South Wales, Australia
- Intergrown with ktenasite forming fibrous and botryoidal crusts and coatings less than 0.1 mm thick, at the Kintore Open Cut, Broken Hill, New South WalesBroken Hill, New South Wales-Geology:Broken Hill's massive orebody, which formed about 1,800 million years ago, has proved to be among the world's largest silver-lead-zinc mineral deposits. The orebody is shaped like a boomerang plunging into the earth at its ends and outcropping in the centre. The protruding tip of the...
, Australia - Associated with a new mineral mallestigite, reported in 2004, near CarinthiaCarinthia (state)Carinthia is the southernmost Austrian state or Land. Situated within the Eastern Alps it is chiefly noted for its mountains and lakes.The main language is German. Its regional dialects belong to the Southern Austro-Bavarian group...
, Austria, on the dump of a copper-lead-zinc mine. The mallestigite formed in fractures during weathering of primary galenaGalenaGalena 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...
and tetrahedriteTetrahedriteTetrahedrite is a copper antimony sulfosalt mineral with formula: 12Sb4S13. It is the antimony endmember of the continuous solid solution series with arsenic bearing tennantite. Pure endmembers of the series are seldom if ever seen in nature. Of the two, the antimony rich phase is more common...
. Other associated minerals were anglesiteAnglesiteAnglesite is a lead sulfate mineral with the chemical formula PbSO4. It occurs as an oxidation product of primary lead sulfide ore, galena. Anglesite occurs as prismatic orthorhombic crystals and earthy masses, and is isomorphous with barite and celestine. It contains 74% of lead by mass and...
, brochantiteBrochantiteBrochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is CuSO4·3Cu2. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it is named for its discoverer, the French geologist and mineralogist, A. J. M...
, linariteLinariteLinarite is a somewhat rare, crystalline mineral that is known among mineral collectors for its unusually intense, pure blue color. It is formed by the oxidation of galena and chalcopyrite and other copper sulfides. It is a combined copper lead sulfate hydroxide with formula PbCuSO42.Linarite...
and schultenite - At Silver Gill, Caldbeck Fells, CumbriaCumbriaCumbria , is a non-metropolitan county in North West England. The county and Cumbria County Council, its local authority, came into existence in 1974 after the passage of the Local Government Act 1972. Cumbria's largest settlement and county town is Carlisle. It consists of six districts, and in...
, England, partly altered to brochantiteBrochantiteBrochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is CuSO4·3Cu2. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it is named for its discoverer, the French geologist and mineralogist, A. J. M...
, Cu4SO4(OH)6 - As microcrystals in small vugs in prehnitePrehnitePrehnite is a phyllosilicate of calcium and aluminium with the formula: Ca2Al2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most oftens forms as stalactitic or botryoidal aggregates, with only just the crests of small...
-quartzQuartzQuartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
vein sections at the Clark Mine, Keweenaw PeninsulaKeweenaw PeninsulaThe Keweenaw Peninsula is the northern-most part of Michigan's Upper Peninsula. It projects into Lake Superior and was the site of the first copper boom in the United States. As of the 2000 census, its population was roughly 43,200...
, Michigan, USA