Sphalerite

sphalerite

galena

zinc

wurtzite

Images

Formula: ZnS
Sulphide, sphalerite group, isometric polytype of trigonal or hexagonal wurtzite. Wurtzite is the high temperature polytype; the transition for pure ZnS occurs at 1020^oC, and this transition temperature is lowered by the presence of iron in solid solution ( AM 46.1382).

Varieties

Cleiophane is a light-coloured to colourless variety of sphalerite with low Fe and Mn content

Properties of Sphalerite Crystal System: Isometric br Specific gravity: 3.9 to 4.1 measured, 4.096 calculated
Hardness: 3½ to 4
Streak: White, yellow to brown if iron is present
Colour: Yellow, brown, red, green, black, rarely colourless
Solubility: Moderately soluble in hydrochloric acid; slightly soluble in nitric acid; insooluble in water
Common impurities: Mn,Cd,Hg,In,Tl,Ga,Ge,Sb,Sn,Pb,Ag
Environments:

Igneous environments
Pegmatites
Carbonatites
Sedimentary environments
Metamorphic environments
Hydrothermal environments

Sphalerite is extremely common. Its occurrence and mode of origin are similar to those of galena, with which it is commonly found. Sphalerite occurs in granite, gabbro, sedimentary deposits and contact metamorphic deposits. It is found as a primary mineral in hypothermal (high temperature) hydrothermal veins associated with arsenopyrite, galena and quartz, and in replacement deposits associated with chalcopyrite, galena and pyrite.
Sphalerite with only minor galena occurs associated with pyrrhotite, pyrite and magnetite.
It also may be found in gabbro and granite.
In the oxidised zone of epithermal veins, sphalerite (primary) alters to secondary hemimorphite, smithsonite and manganese-bearing willemite.

Localities

The Two Mile and Three Mile deposits, Paddy's River, Paddys River District, Australian Capital Territory, Australia, are skarn deposits at the contact between granodiorite and volcanic rocks. Sphalerite is a primary sulphide that occurs as aggregates in chloritic rocks at the Two Mile deposit. Associated minerals include chalcopyrite and galena (AJM 22.1.37-38).

At the Mount Kelly deposit, Gunpowder District, Queensland, Australia, the deposit has been mined for oxide and supergene copper ores, predominantly malachite, azurite and chrysocolla. The ores overlie primary zone mineralisation consisting of quartz-dolomite-sulphide veins hosted in dolomite-bearing siltstone and graphitic schist.
Sphalerite occurs rarely rimming pyrite and chalcopyrite and as inclusions in pyrite. Paragenesis for the primary zone is dolomite followed by pyrite, then chalcopyrite and sphalerite, and lastly bornite (AJM 22.1.20 & 25).

At the Mount Deverell variscite deposit, Milgun Station, Western Australia, rare grains of sphalerite have been found as inclusions in grains of quartz in siltstone enclosing variscite veins. The variscite deposits are hosted by marine sedimentary rocks (AJM 20.2.29).

At the Blue Points mine, Thunder Bay, Ontario, Canada, sphalerite is associated with calcite and minor chalcopyrite in silicified mudstone breccia (R&M 94.4.330).

At the Lin Ma Hang mine, North District, New Territories, Hong Kong, China, the lead-zinc deposit is a hydrothermal deposit which lies along a fault zone within altered acid volcanic rocks, consisting mainly of chlorite, biotite, sericite and actinolite, with scattered quartz. (Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)
The mineralisation consists of a series of fissure vein deposits varying from a few mm to several metres on width. The initial vein filling was coarse milky quartz. this was followed by an intrusion of fine-grained quartz carrying the metallic minerals, galena, pyrite, sphalerite and chalcopyrite, in order of abundance (Geological Society of Hong Kong Newsletter, 9.4.3-27).

At Devil's Peak, Sai Kung District, New Territories, Hong Kong, China, the mineralisation occurred in quartz veins in the contact zone between a granite intrusion and acid volcanic rocks. The mine is now closed, and inaccessible for collecting. Sphalerite occurred in some of the beryl-wolframite containing quartz veins (Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)

The Needle Hill Mine, Needle Hill, Sha Tin District, New Territories, Hong Kong, China, is a tungsten mine, abandoned in 1967. The principal ore is wolframite, and the principal gangue mineral is quartz. Molybdenum also occurs. The mineralisation consists of a series of parallel fissure veins that cut through granite. Wolframite and quartz are the main minerals, but galena, sphalerite, pyrite, molybdenite and fluorite have also been found here (Geological Society of Hong Kong Newsletter 9.3.29-40). The quartz-wolframite veins are of high-temperature hydrothermal formation, and grade into wolframite-bearing pegmatites.
Sphalerite is a common accessory mineral in the wolframite-bearing quartz veins and pegmatites (Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)

At Chuen Lung, Tsuen Wan District, New Territories, Hong Kong, China, in fissure veins in granite rocks in a small stream near Chuen Lung, silver-bearing galena occurs associated with massive granular amber coloured sphalerite, chalcopyrite, pyrite and pyrrhotite (Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)

The Lin Fa Shan deposit, Tsuen Wan District, New Territories, Hong Kong, China, is located in a remote area of the Tai Mo Shan Country Park, on a steep west facing slope of Lin Fa Shan, just above the abandoned village of Sheung Tong. The surrounding hillsides are covered with shallow excavations, representing past searches for wolframite, the natural ore of tungsten. The abandoned workings are extremely dangerous with unsupported tunnels, open shafts and no maintenance since their closures in 1957; the workings should not be entered (http://industrialhistoryhk.org/lin-shan).
Sphalerite is common in wolframite-bearing quartz veins (Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council).

At the Xiling Mine, Gongcheng County, Guilin, Guangxi, China, many patches of yellow brown, vitreous opaque crystalline sphalerite occur in calcite veins which have intruded into a dark coloured matrix (AESS).
Sphalerite from Xiling

At the Lingchuan Mine, Lingchuan County, Guilin, Guangxi, China, a band of crystalline sphalerite 1 cm wide has been found, in a quartz vein intruding an almost black matrix (AESS).
Sphalerite from Lingchuan - Image

At the Chashan Mine, Xianghualing Sn-polymetallic ore field, Linwu County, Chenzhou, Hunan, China, of dark brown sphalerite occurs (AESS).
Sphalerite from Chashan - Image

At the Xianghuapu Mine, Xianghualing Sn-polymetallic ore field, Linwu County, Chenzhou, Hunan, China, a specimen has been found, 7.5 cm x 5.5 cm x 6 cm, from a low temperature sulphide vein, with black metallic crystals sphalerite variety marmatite, small clear crystals of fluorite and also some brass-yellow pyrite and galena, with greenish bands of chlorite from the host rock (AESS).
Sphalerite from Xianghuapu

At the Manaoshan Mine, Dongpo ore field, Suxian District, Chenzhou, Hunan, China, dark brown chrystalline sphalerite occurs with greenish white fluorite that fluoresces in long wave and in short wave UV (AESS).
Sphalerite from Manaoshan - Image

At the Ganluo Mine, about 30 minutes from Ganluo Town, Ganluo County, Liangshan Yi, Sichuan, China, massive, dark brown, crystalline sphalerite has been found (AESS).
Sphalerite from Ganluo - Image

At Charcas, Charcas Municipality, San Luis Potosí, Mexico, the primary minerals are sphalerite, galena, chalcopyrite, bornite, tetrahedrite, arsenopyrite, pyrite and silver minerals such as jalpaite, diaphorite and acanthite. In the host rock, as metamorphic or alteration minerals, danburite, datolite, hedenbergite, epidote, chlorite, andradite, actinolite and wollastonite have been reported.
Quartz, calcite and danburite crystallised during the entire life of the systems, throughout the intrusive emplacement, metamorphism, and mineralising events. With depth, both sphalerite and galena decrease while chalcopyrite increases.
Secondary sulphides formed include bornite, covellite, digenite and chalcocite. Native silver, native gold, hematite and goethite were deposited after the sulphides (Minrec 55.6.727-728).
Sphalerite is ubiquitous in the Charcas mines, as the main ore of zinc. It occurs abundantly in massive form and was occasionally found as crystals in cavities or open fractures. The crystals are dark brown to black with a brilliant lustre, and can reach 6 cm in size. Sphalerite is associated with other sulphides such as galena, pyrite and chalcopyrite, and also with gangue minerals such as datolite, calcite, quartz and danburite (Minrec 55.6.770).
Sphalerite from Charcas - Image

At Berg Aukas, Grootfontein, Otjozondjupa Region, Namibia, sphalerite is partially oxidised from near-surface to depths of around 600 m. It contains trace amounts of iron, cadmium, manganese and germanium (R&M 96.2.136-140) The paragenetic sequence for the sulphides is proposed to be pyrite (oldest) - bornite - chalcopyrite - tennantite-sphalerite-galena-enargite-germanite-renierite-tetrahedrite - jordanite (youngest) (R&M 96.2.113)
Sphalerite from Berg Aukas - Image

At the Free State Geduld Mine, Welkom, Lejweleputswa District, Free State, South Africa, the largest sphalerite crystals from southern Africa, measuring up to 6.2 cm, have been collected from a fault zone. Associated minerals include pyrrhotite, pyrite, quartz and galena (R&M 96.4.343).
Sphalerite from the Free State Geduld Mine - Image

At the Randfontein Estates Mine, West Rand District, Gauteng, South Africa, a specimen of yellow baryte overgrown on tetrahedral, striated sphalerite has been found (R&M 96.4.343).
Sphalerite from the Randfontein Estates Mine - Image

At the Mponeng Mine, West Wits, Far West Rand, West Rand District Municipality, Gauteng, South Africa, finely crystallised sphalerite has been found forming rims on the edges of pyrrhotite or partially coating galena, also some large individual stepped tetrahedral crystals of sphalerite to 3 cm have been found. Cleavage fragments yield a ruby-red translucency (R&M 96.4.343).
Sphalerite from the Mponeng Mine - Image

At Aggeneys, Namakwa, Northern Cape, South Africa, siderite pseudomorphs after sphalerite have been found (KL p160).
Sphalerite from Aggeneys - Image

At Alderley Edge, Cheshire, England, UK, copper mineralised solutions percolated through porous sandstone and deposited barium, cobalt, copper, lead, vanadium and zinc minerals between the sand grains. Anhydrite formed as cement in permeable rocks, then baryte was deposited, followed by pyrite, chalcopyrite, sphalerite and galena (RES pps 49-50).

At the Boltsburn Mine, Rookhope, Weardale, County Durham, England, UK, sphalerite is associated with fluorite (SY p172)

At Force Crag Mine, Coledale, Above Derwent, Allerdale, Cumbria, England, UK, a specimen has been found with a quartz matrix covered with a combination of matte black sphalerite, white cerussite and typical brownish pyromorphite (AESS).
Sphalerite from Force Crag - Image

At Alston Moor, Eden, Cumbria, England, UK, sphalerite is associated with ankerite and fluorite (SY p172)

At the Brownley Hill Mine, Nenthead, Alston Moor, Eden, Cumbria, England, UK, a specimen 4.4 x 3.2 3.1 cm³ has been found with a group of dark root beer brown, lustrous, sharp sphalerite crystals with metallic grey modified cuboctahedral galena crystals on a calcite and drusy quartz matrix. The largest sphalerite crystals are up to 7 mm across (AESS).
Sphalerite from Brownley Hill - Image

At Carrs Mine, Nenthead, Alston Moor, Eden, Cumbria, England, UK, a specimen is 3.2 × 5.7 × 2.3 cm³ has been found with a matrix lined with clear to white prismatic quartz studded with larger semi-bright complex crystals of sphalerite, the largest being 1.3 cm in size. Ankerite and galena are also present (AESS).
Sphalerite from Carrs Mine - Image

In a cavity at the Smallcleugh Mine, Nenthead, Alston Moor, Eden, Cumbria, England, UK, sphalerite, rarely, seems to have grown around pyrite, indicating that pyrite was formed earlier in the paragenetic sequence. Both pyrite and sphalerite commonly occur directly on quartz. Rarely, sphalerite occurs entirely supported by ankerite; it is not clear whether this is late-stage growth or whether crystals have detached from above and fallen onto the ankerite. Sphalerite crystals are highly irregular and reach 12 mm across. Some show slight oxidation (JRS 18.20).
It has been found here in association with calcite, and is often highly lustrous. On one specimen it was found with calcite on quartz with some pyrite and a patch of white fluorite with a covering of brianyoungite. The calcite fluoresces pink under long wave UV and the fluorite fluoresces blue under short wave (AESS).
Sphalerite from Smallcleugh - Image

At the Nentsberry Haggs Mine, Alston Moor, Eden, Cumbria, England, UK, a specimen has been found with almost black, vitreous, opaque crystals of sphalerite up to 9 mm across, and light grey, dull, opaque crystals of galena to 5 mm across. There is also some dark brown ankerite (AESS).
Sphalerite from Nentsberry Haggs - Image

At the Gregory mine, Ashover, Derbyshire, England, UK, sphalerite is associated with fluorite (RES p102, 103).

At the Odin mine, Castleton, Derbyshire, England, UK, sphalerite is associated with fluorite and baryte (RES p130).

At Millclose mine, Darley Dale, Derbyshire, England, UK, sphalerite is associated with pyrite, fluorite and calcite (RES p93, 95).
Sphalerite from the Millclose Mine - Image

At Eyam, Derbyshire, England, UK, sphalerite is associated with calcite, fluorite and galena (RES p117).

At Ladywash mine, Eyam, Derbyshire, England, UK, sphalerite is associated with fluorite and pyrite (RES p120).
Sphalerite from the Ladywash Mine - Image

At Cloud Hill quarry, Breedon on the Hill, Leicestershire, England, UK, sphalerite is associated with calcite, baryte and chalcopyrite in dolomitised limestone (RES p207).

At Lord Ferrer's mine, Staunton Harold, Ashby-de-la-Zouch, Leicestershire, England, UK, sphalerite is associated with galena, chalcopyrite, calcite, baryte and dolomite (RES p222).

At Barrasford Quarry, Chollerton, Northumberland, England, UK, veins of calcite up to 10 mm wide contain abundant masses of sphalerite up to 20 mm across, accompanied by patches of galena and, more rarely, with chalcopyrite and pyrrhotite (JRS 21.14).

At the Callow Hill quarry, Pontesbury, Shropshire, England, UK, sphalerite has been found in quartz veinstone associated with galena (RES p291).
Sphalerite from Callow Hill - Image

At Judkins quarry, Nuneaton, Warwickshire, England, UK, sphalerite is associated with baryte and calcite (RES p325).
Sphalerite from Judkins Quarry - Image

At Roar Hill, Ballater, Buchan Grampian, Scotland, UK, lead-bearing vein mineralisation was exposed during recent work carried out on an unmetalled vehicle track. A small temporary quarry exposed fluorite-bearing quartz veins and minor wulfenite in light-coloured granite. At a second site, a little further to the west, an oxidised galena-bearing quartz vein was exposed.
Sphalerite occurs as honey-brown crystals and cleavages in partly corroded galena at the track exposure. It is much less common than galena. No zinc-bearing supergene minerals have been found at either site (JRS 22.33).

The Nelly James Mine, Miller Canyon, Miller Peak, Cochise County, Arizona, USA, is a former small surface lead, copper, zinc, gold and silver mine located at an altitude of 7250 feet. Mineralisation is a vein deposit Mindat). The mine is now famous for fluorescent minerals collected from the dumps, including calcite (fluoresces red), hydrozincite (sky blue), powellite (creamy-yellow), smithsonite (crimson red), sphalerite (yellow-orange) and willemite (green).
Sphalerite when fine-grained is colourless to tan in daylight, but when coarsely crystalline it has a shiny metallic lustre and can be brown, silver or almost black. Under longwave UV the response is bright yellow-orange. Some specimens exhibit a delayed fluorescent response and tend to get brighter over a short period of time. Under shortwave UV the response is a weak yellow-orange. Under medium range UV the response is also yellow-orange but with a medium brightness. Sphalerite also exhibits a long-duration sustained luminescence upon removal of the longwave UV source (R&M 97.1.48-56).
Sphalerite from the Nelly James Mine - Image

At the Magma mine, Pioneer District, Pinal county, Arizona, USA, sphalerite has been found, usually on chalcopyrite but sometimes on quartz crystals, and associated with baryte and gypsum (R&M 95.1.87-88).
Sphalerite from the Magma Mine - Image

At the Philadelphia mine, Arkansas, USA, smithsonite pseudomorphs after sphalerite have been found with dolomite (KL p170).

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, sphalerite crystals have been found in massive rhodochrosite associated with perloffite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.515).

At Jopline, Missouri, USA, tetragonal crystals of chalcopyrite have been found epitaxial on sphalerite (FM 47452).
Sphalerite from Joplin - Image

At the PC Mine, Cataract Mining District, Jefferson county, Montana, USA, sphalerite occurred as gemmy green or brown crystals to 23 cm, with the largest crystal weighing 3.2 kilograms (R&M 96.6.494-496).
Sphalerite from the PC Mine - Image

At Cookes Peak mining district, Luna county, New Mexico, USA, sphalerite was the principal source for zinc in secondary smithsonite. Unoxidised masses occur most often with pyrite and galena in replacement pods in dolomite (R&M 94.3.236).

At the Keyes Mica Quarries, Orange, Grafton County, New Hampshire, USA, the pegmatites are beryl-type rare-element (RE) pegmatites.
The Number 1 mine exposed a pegmatite that shows the most complex zonation and diverse mineralogy of any of the Keyes pegmatites. Six zones are distinguished, as follows, proceeding inward from the margins of the pegmatite:
(1) quartz-muscovite-plagioclase border zone, 2.5 to 30.5 cm thick
(2) plagioclase-quartz-muscovite wall zone, 0.3 to 2.4 metres thick
(3) plagioclase-quartz-perthite-biotite outer intermediate zone, 0.3 to 5.2 metres thick, with lesser muscovite
(4) quartz-plagioclase-muscovite middle intermediate zone, 15.2 to 61.0 cm thick
(5) perthite-quartz inner intermediate zone, 0.9 to 4.6 meters thick
(6) quartz core, 1.5 to 3.0 metres across
The inner and outer intermediate zones contained perthite crystals up to 1.2 meters in size that were altered to vuggy albite-muscovite with fluorapatite crystals. This unit presumably was the source of the albite, muscovite, fluorapatite, quartz and other crystallised minerals found in pieces of vuggy albite rock on the dumps next to the mine.
The middle intermediate zone produced sheet mica with accessory minerals including tourmaline, graftonite, triphylite, vivianite, pyrite, pyrrhotite, and beryl crystals to 30.5 cm long and 12.7 cm across.
A 7-mm patch of lustrous black sphalerite embedded in massive triphylite with microsized hureaulite and phosphosiderite or strengite crystals has been collected at the Keyes No. 1 mine (R&M 97.4.325).

At the Big Chief Mine, Glendale, Keystone Mining District, Pennington county, South Dakota, USA, sphalerite occurs with arsenopyrite and quartz (R&M 49.7-8.435-438).

At the Empire State No. 4 Mine, Balmat, Balmat-Edwards Zinc Mining District, St. Lawrence County, New York, USA, gemmy, honey-coloured crystals of sphalerite have been found (MinRec 55.3.355).
Sphalerite from the Empire State No. 4 Mine - Image

The Purple Diopside Mound, Rose Road, Pitcairn, St. Lawrence county, New York, USA, is situated in marble. The development of veins of large crystals probably occurred as a result of fluid penetration from a concurrent intrusion. Many of the minerals of interest to collectors formed during this primary event, with additional species resulting from the subsequent alteration of scapolite. There seems to be little, if any, secondary, late-stage mineralisation present.
Sphalerite occurs as dark brown submillimetre grains that are spatially associated with corundum (R&M 96.6.552).

At the Stoneco White Rock Quarry, Clay Center, Allen Township, Ottawa county, Ohio, USA, although uncommon, twinned tetrahedral orange-red sphalerite crystals have been found (R&M 97.3.277).
Sphalerite from the Stoneco White Rock Quarry - Image

At the SK Star #2 Mining Claim, The Cove, Topaz Mountain, Thomas Range, Juab County, Utah, USA, sphalerite, occurring as minute crystals in the fault zone, fluoresces a golden yellow or orange in shortwave UV (MinRec 51.6.809-810).

Alteration

Sphalerite is a paramorph of wurtzite. The transition from sphalerite to wurtzite occurs around 1020^oC.

Oxidation of pyrite forms ferrous (divalent) sulphate and sulphuric acid:
pyrite + oxygen + H₂O → ferric sulphate + sulphuric acid
FeS₂ + 7O + H₂O → FeSO₄ + H₂SO₄

The ferrous (divalent) sulphate readily oxidizes to ferric (trivalent) sulphate and ferric hydroxide:
ferrous sulphate + oxygen + H₂O → ferric sulphate + ferric hydroxide
6FeSO₄ + 3O + 3H₂O → 2Fe₂(SO₄)₃ + 2Fe(OH)₃
Ferric sulfate is a strong oxidizing agent; it attacks sphalerite as below:

sphalerite, ferric sulphate and water to zinc sulphate, ferrous sulphate and sulphuric acid
ZnS + 4Fe₂(SO₄)₃ + 4H₂O → ZnSO₄ + 8FeSO₄ + 4H₂SO₄
(AMU/b3-3-7.htm)

skinnerite and sphalerite = Zn-tetrahedrite and chalcocite
4Cu₃SbS₃ + 2ZnS → Cu₁₀Zn₂Sb₄S₁₃ + Cu₂S
(CM 28.725-738)

sphalerite to covellite: Because covellite is less soluble than sphalerite, supergene covellite may form below the zone of oxidation when dissolved copper ions Cu²⁺ replace zinc ions Zn²⁺ from sphalerite.
Cu²⁺ + sphalerite → covellite + Zn²⁺
Cu²⁺ + ZnS → CuS + Zn²⁺
(KB p527)

Zn-tetrahedrite to chalcocite, antimony, sphalerite and sulphur
Cu₁₀Zn₂Sb₄S₁₃ → 5Cu₂S + 4Sb + 2ZnS + 3S₂
(CM 28.725-738)

Zn-tetrahedrite to skinnerite, antimony, sphalerite and sulphur
3Cu₁₀Zn₂Sb₄S₁₃ → 10Cu₃SbS₃ + 2Sb + 6ZnS + 3/2S₂
(CM 28.725-738)

Zn-tetrahedrite to skinnerite, stibnite and sphalerite
3Cu₁₀Zn₂Sb₄S₁₃ → 10Cu₃SbS₃ + Sb₂S₃ +6ZnS
(CM 28.725-738)

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