Strontianite

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Strontianite
Mineraly.sk - stroncianit.jpg
Strontianite from Slovakia
General
Category Carbonate minerals
Formula
(repeating unit)
SrCO3
IMA symbol Str [1]
Strunz classification 5.AB.15 (10 ed)
5/B.04-20 (8 ed)
Dana classification14.01.03.03
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pmcn
Unit cell a = 5.1  Å, b = 8.4 Å
c = 6.0 Å; Z = 4
Identification
Formula mass 147.63 g/mol
ColorColourless, white, gray, light yellow, green or brown; colourless in transmitted light
Crystal habit Prismatic, acicular, pseudo hexagonal, columnar to fibrous, granular, massive
Twinning Very common, usually contact, rarely penetration, also repeated
Cleavage {110} nearly perfect, {021} poor, {010} traces
Fracture Subconchoidal to uneven
Tenacity Brittle
Mohs scale hardness3+12
Lustre Vitreous, resinous on breaks, greasy
Streak White
Diaphaneity Transparent to translucent
Specific gravity 3.74 to 3.78 Transparent versions are heavier than the other ones
Optical propertiesBiaxial (−)
Refractive index nα = 1.52, nβ = 1.66, nγ = 1.67
Birefringence 0.15
2V angle Measured: 7°, Calculated: 12° to 8°
Ultraviolet fluorescence Almost always fluorescent
Solubility Soluble in dilute HCl
Alters toCelestine SrSO4
References [2] [3] [4] [5]

Strontianite (Sr C O 3) is an important raw material for the extraction of strontium. It is a rare carbonate mineral and one of only a few strontium minerals. It is a member of the aragonite group.

Contents

Aragonite group members: [2] aragonite (CaCO3), witherite (BaCO3), strontianite (SrCO3), cerussite (PbCO3)

The ideal formula of strontianite is SrCO3, with molar mass 147.63 g, [4] but calcium (Ca) can substitute for up to 27% of the strontium (Sr) cations, and barium (Ba) up to 3.3%. [2]

The mineral was named in 1791 for the locality, Strontian, Argyllshire, Scotland, where the element strontium had been discovered the previous year. [2] Although good mineral specimens of strontianite are rare, strontium is a fairly common element, with abundance in the Earth's crust of 370 parts per million by weight, 87 parts per million by moles, much more common than copper with only 60 parts per million by weight, 19 by moles. [6] Strontium is never found free in nature. The principal strontium ores are celestine SrSO4 and strontianite SrCO3. The main commercial process for strontium metal production is reduction of strontium oxide with aluminium. [6]

Unit cell

Strontianite is an orthorhombic mineral, belonging to the most symmetrical class in this system, 2/m 2/m 2/m, whose general form is a rhombic dipyramid. The space group is Pmcn. There are four formula units per unit cell (Z = 4) and the unit cell parameters are a = 5.1 Å, b = 8.4 Å, c = 6.0 Å.

Structure

Strontianite is isostructural with aragonite. [7] When the CO3 group is combined with large divalent cations with ionic radii greater than 1.0 Å, the radius ratios generally do not permit stable 6-fold coordination. For small cations the structure is rhombohedral, but for large cations it is orthorhombic. This is the aragonite structure type with space group Pmcn. In this structure the CO3 groups lie perpendicular to the c axis, in two structural planes, with the CO3 triangular groups of one plane pointing in opposite directions to those of the other. [7] These layers are separated by layers of cations. [2]

The CO3 group is slightly non-planar; the carbon atom lies 0.007 Å out of the plane of the oxygen atoms. The groups are tilted such that the angle between a plane drawn through the oxygen atoms and a plane parallel to the a-b unit cell plane is 2°40’. [8]

Crystal form

Strontianite occurs in several different habits. Crystals are short prismatic parallel to the c axis and often acicular. [2] [3] [5] Calcium-rich varieties often show steep pyramidal forms. [2] Crystals may be pseudo hexagonal [2] [3] [5] due to equal development of different forms. [3] Prism faces are striated horizontally. [2] [3] The mineral also occurs as columnar to fibrous, granular or rounded masses. [2] [3] [5]

Strontianite-Calcite-Fluorite-274999.jpg
Radial aggregate of strontianite
Strontianite-283289.jpg
Acicular strontianite in spherical aggregates
Strontianite-ww3c.jpg
Strontianite in pseudo-hexagonal crystals

Optical properties

Strontianite is colourless, white, gray, light yellow, green or brown, colourless in transmitted light. It may be longitudinally zoned. It is transparent to translucent, with a vitreous (glassy) lustre, resinous on broken surfaces, and a white streak.

It is a biaxial(−) mineral. The direction perpendicular to the plane containing the two optic axes is called the optical direction Y. In strontianite Y is parallel to the b crystal axis. The optical direction Z lies in the plane containing the two optic axes and bisects the acute angle between them. In strontianite Z is parallel to the a crystal axis. The third direction X, perpendicular both to Y and to Z, is parallel to the c crystal axis. [2] [5] The refractive indices are close to nα = 1.52, nβ = 1.66, nγ = 1.67, with different sources quoting slightly different values:

The maximum birefringence δ is 0.15 [3] and the measured value of 2V is 7°, calculated 12° to 8°. [3] [4]

If the colour of the incident light is changed, then the refractive indices are modified, and the value of 2V changes. This is known as dispersion of the optic axes. For strontianite the effect is weak, with 2V larger for violet light than for red light r < v. [5]

Luminescence

Strontianite is almost always fluorescent. [3] It fluoresces bright yellowish white under shortwave, mediumwave and longwave ultraviolet radiation. If the luminescence persists after the ultraviolet source is switched off the sample is said to be phosphorescent. Most strontianite phosphoresces a strong, medium duration, yellowish white after exposure to all three wavelengths. [10] It is also fluorescent and phosphorescent in X-rays and electron beams. All materials will glow red hot if they are heated to a high enough temperature (provided they do not decompose first); some materials become luminescent at much lower temperatures, and this is known as thermoluminescence. Strontianite is sometimes thermoluminescent. [2] [3] [5]

Physical properties

Cleavage is nearly perfect parallel to one set of prism faces, {110}, and poor on {021}. Traces of cleavage have been observed on {010}. [3] [5]

Twinning is very common, with twin plane {110}. The twins are usually contact twins; in a contact twin the two individuals appear to be reflections of each other in the twin plane. Penetration twins of strontainite are rarer; penetration twins are made up of interpenetrating individuals that are related to each other by rotation about a twin axis. Repeated twins are made up of three or more individuals twinned according to the same law. If all the twin planes are parallel then the twin is polysynthetic, otherwise it is cyclic. [7] In strontianite repeated twinning forms cyclic twins with three or four individuals, or polysynthetic twins. [2] [3] [5]

The mineral is brittle, and breaks with a subconchoidal to uneven fracture. It is quite soft, with a Mohs hardness of 3+12, [3] between calcite and fluorite. The specific gravity of the pure endmember with no calcium substituting for strontium is 3.78, [9] but most samples contain some calcium, which is lighter than strontium, giving a lower specific gravity, in the range 3.74 to 3.78. [3] Substitutions of the heavier ions barium and/or lead increase the specific gravity, although such substitutions are never very abundant. [9] Strontianite is soluble in dilute hydrochloric acid HCl [2] [3] and it is not radioactive. [4]

Environment and associations

Strontianite is an uncommon low-temperature hydrothermal mineral formed in veins in limestone, marl, and chalk, and in geodes and concretions. It occurs rarely in hydrothermal metallic veins but is common in carbonatites. [5] It most likely crystallises at or near 100 °C. Its occurrence in open vugs and veins suggests crystallisation at very low pressures, probably at most equal to the hydrostatic pressure of the ground water. [9] Under appropriate conditions it alters to celestine SrSO4, and it is itself found as an alteration from celestine. [2] These two minerals are often found in association, together with baryte, calcite, harmotome and sulfur. [5]

Occurrences

Type locality

The type locality is Strontian, North West Highlands (Argyllshire), Scotland, UK. The type material occurred in veins in gneiss. [2]

Other UK localities include Brownley Hill Mine (Bloomsberry Horse Level), Nenthead, Alston Moor District, North Pennines, North and Western Region (Cumberland), Cumbria, England, associated with a suite of primary minerals (bournonite, millerite and ullmannite) which are not common in other Mississippi Valley-type deposits. [11]

Canada

The Francon quarry, Montréal, Québec.
Strontianite is very common at the Francon Quarry, in a great variety of habits. It is a late stage mineral, sometimes found as multiple generations. It is found as translucent to opaque, white to pale yellow or beige generally smooth surfaced spheroids, hemispheres and compact spherical and botryoidal aggregates to 10 cm in diameter, and as spheres consisting of numerous radiating acicular crystals, up to 1 cm across. Also as tufts, parallel bundles, and sheaf-like clusters of fibrous to acicular crystals, and as white, finely granular porcelaneous and waxy globular aggregates. Transparent, pale pink, columnar to tabular sixling twins up to 1 cm in diameter have been found, and aggregates of stacked stellate sixling twins consisting of transparent, pale yellow tabular crystals. [10]

Another Canadian occurrence is at Nepean, Ontario, in vein deposits in limestone. [2]

Germany

Commercially important deposits occur in marls in Westphalia, [2] and it is also found with zeolites at Oberschaffhausen, Bötzingen, Kaiserstuhl, Baden-Württemberg. [2]

India

In Trichy (Tiruchirappalli; Tiruchi), Tiruchirapalli District, Tamil Nadu, it occurs with celestine SrSO4, gypsum and phosphate nodules in clay. [2]

Mexico

It occurs in the Sierra Mojada District, with celestine in a lead-silver deposit. [2]

Russia

It occurs in the Kirovskii apatite mine, Kukisvumchorr Mt, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, in late hydrothermal assemblages in cavities in pegmatites, associated with kukharenkoite-(La), microcline, albite, calcite, nenadkevichite, hilairite, catapleiite, donnayite-(Y), synchysite-(Ce), pyrite and others. [12]

It also occurs at Yukspor Mountain, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, in an aegerine-natrolite-microcline vein in foyaite, associated with aegirine, anatase, ancylite-(Ce), barylite, catapleiite, cerite-(Ce), cerite-(La), chabazite-(Ca), edingtonite, fluorapatite, galena, ilmenite, microcline, natrolite, sphalerite and vanadinite. [13] At the same locality it was found in alkaline pegmatite veins associated with clinobarylite, natrolite, aegirine, microcline, catapleiite, fluorapatite, titanite, fluorite, galena, sphalerite, annite, astrophyllite, lorenzenite, labuntsovite-Mn, kuzmenkoite-Mn, cerite-(Ce), edingtonite, ilmenite and calcite. [14]

United States

In the Gulf coast of Louisiana and Texas, strontianite occurs with celestine in calcite cap rock of salt domes. [2]

At the Minerva Number 1 Mine (Ozark-Mahoning Number 1 Mine) Ozark-Mahoning Group, Cave-in-Rock, Illinois, in the Kentucky Fluorspar District, Hardin County strontanite occurs as white, brown or rarely pink tufts and bowties of acicular crystals with slightly curved terminations. [15]

In the Silurian Lockport Group, Central and Western New York strontianite is observed in cavities in eastern Lockport, where it occurs as small white radiating sprays of acicular crystals. [16]

In Schoharie County, New York, it occurs in geodes and veins with celestine and calcite in limestone, [2] and in Mifflin County, Pennsylvania, it occurs with aragonite, again in limestone. [2]

See also

Related Research Articles

<span class="mw-page-title-main">Celestine (mineral)</span> Sulfate mineral

Celestine (the IMA-accepted name) or celestite is a mineral consisting of strontium sulfate (SrSO4). The mineral is named for its occasional delicate blue color. Celestine and the carbonate mineral strontianite are the principal sources of the element strontium, commonly used in fireworks and in various metal alloys.

<span class="mw-page-title-main">Weloganite</span>

Weloganite is a rare carbonate mineral with formula: Na2(Sr,Ca)3Zr(CO3)6·3H2O. It was discovered by Canadian government mineralogist Ann P. Sabina in 1967 and named for Canadian geologist Sir William Edmond Logan (1798–1875). It was first discovered in Francon Quarry, Montreal, Quebec, Canada and has only been reported from a few localities worldwide.

<span class="mw-page-title-main">Creedite</span>

Creedite is a calcium aluminium sulfate fluoro hydroxide mineral with formula: Ca3Al2SO4(F,OH)10·2(H2O). Creedite forms colorless to white to purple monoclinic prismatic crystals. It often occurs as acicular radiating sprays of fine prisms. It is translucent to transparent with indices of refraction of nα = 1.461 nβ = 1.478 nγ = 1.485. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 2.7.

<span class="mw-page-title-main">Vivianite</span> Phosphate mineral

Vivianite (Fe2+
3
(PO
4
)
2
·8H
2
O
) is a hydrated iron phosphate mineral found in a number of geological environments. Small amounts of manganese Mn2+, magnesium Mg2+, and calcium Ca2+ may substitute for iron Fe2+ in the structure. Pure vivianite is colorless, but the mineral oxidizes very easily, changing the color, and it is usually found as deep blue to deep bluish green prismatic to flattened crystals.
Vivianite crystals are often found inside fossil shells, such as those of bivalves and gastropods, or attached to fossil bone.

<span class="mw-page-title-main">Alstonite</span>

Alstonite, also known as bromlite, is a low temperature hydrothermal mineral that is a rare double carbonate of calcium and barium with the formula BaCa(CO
3
)
2
, sometimes with some strontium. Barytocalcite and paralstonite have the same formula but different structures, so these three minerals are said to be trimorphous. Alstonite is triclinic but barytocalcite is monoclinic and paralstonite is trigonal. The species was named Bromlite by Thomas Thomson in 1837 after the Bromley-Hill mine, and alstonite by August Breithaupt of the Freiberg Mining Academy in 1841, after Alston, Cumbria, the base of operations of the mineral dealer from whom the first samples were obtained by Thomson in 1834. Both of these names have been in common use.

<span class="mw-page-title-main">Barytocalcite</span>

Barytocalcite is an anhydrous barium calcium carbonate mineral with the chemical formula BaCa(CO3)2. It is trimorphous with alstonite and paralstonite, that is to say the three minerals have the same formula but different structures. Baryte and quartz pseudomorphs after barytocalcite have been observed.

<span class="mw-page-title-main">Gmelinite</span> Zeolite mineral

Gmelinite-Na is one of the rarer zeolites but the most common member of the gmelinite series, gmelinite-Ca, gmelinite-K and gmelinite-Na. It is closely related to the very similar mineral chabazite. Gmelinite was named as a single species in 1825 after Christian Gottlob Gmelin (1792–1860) professor of chemistry and mineralogist from Tübingen, Germany, and in 1997 it was raised to the status of a series.
Gmelinite-Na has been synthesised from Na-bearing aluminosilicate gels. The naturally occurring mineral forms striking crystals, shallow, six sided double pyramids, which can be colorless, white, pale yellow, greenish, orange, pink, and red. They have been compared to an angular flying saucer.

<span class="mw-page-title-main">Leadhillite</span> Lead sulfate carbonate hydroxide mineral

Leadhillite is a lead sulfate carbonate hydroxide mineral, often associated with anglesite. It has the formula Pb4SO4(CO3)2(OH)2. Leadhillite crystallises in the monoclinic system, but develops pseudo-hexagonal forms due to crystal twinning. It forms transparent to translucent variably coloured crystals with an adamantine lustre. It is quite soft with a Mohs hardness of 2.5 and a relatively high specific gravity of 6.26 to 6.55.

<span class="mw-page-title-main">Beryllonite</span>

Beryllonite is a rare sodium beryllium phosphate mineral with formula NaBePO4. The tabular to prismatic monoclinic crystals vary from colorless to white or pale yellowish, and are transparent with a vitreous luster. Twinning is common and occurs in several forms. It exhibits perfect cleavage in one direction. The hardness is 5.5 to 6 and the specific gravity is 2.8. Refractive indices are nα = 1.552, nβ = 1.558 and nγ = 1.561. A few crystals have been cut and faceted, but, as the refractive index is no higher than that of quartz, they do not make very brilliant gemstones.

<span class="mw-page-title-main">Mesolite</span> Zeolite mineral

Mesolite is a tectosilicate mineral with formula Na2Ca2(Al2Si3O10)3·8H2O. It is a member of the zeolite group and is closely related to natrolite which it also resembles in appearance.

<span class="mw-page-title-main">Nyerereite</span>

Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2Ca(CO3)2. It forms colorless, platey pseudohexagonal orthorhombic crystals that are typically twinned. It has a specific gravity of 2.54 and indices of refraction of nα=1.511, nβ=1.533 and nγ=1.535. Nyerereite is not stable in contact with the atmosphere and rapidly breaks down. Collection specimens must be kept in a sealed argon environment.

<span class="mw-page-title-main">Normandite</span>

Normandite is a brittle orange brown sorosilicate mineral discovered in 1997 by Charles Normand, of Montreal. Normandite occurs in Khibiny Massif, Kola, Russia; in Poudrette quarry, Mont-Saint-Hilaire, Quebec and Tenerife, Canary Islands. It is found in nepheline syenite and in miarolitic cavities in nepheline syenite, associated with nepheline, albite, microcline, aegirine, natrolite, catapleiite, kupletskite, eudialyte, cancrinite, villiaumite, rinkite, and donnayite-(Y).

<span class="mw-page-title-main">Strontium carbonate</span> Chemical compound

Strontium carbonate (SrCO3) is the carbonate salt of strontium that has the appearance of a white or grey powder. It occurs in nature as the mineral strontianite.

<span class="mw-page-title-main">Tuperssuatsiaite</span>

Tuperssuatsiaite is a rare clay mineral found in Greenland, Namibia and Brazil. It is a hydrated phyllosilicate of sodium and iron.

<span class="mw-page-title-main">Magnesiohastingsite</span>

Magnesiohastingsite is a calcium-containing amphibole and a member of the hornblende group. It is an inosilicate (chain silicate) with the formula NaCa2(Mg4Fe3+)(Si6Al2)O22(OH)2 and molar mass 864.69 g. In synthetic magnesiohastingsite it appears that iron occurs both as ferrous iron Fe2+ and as ferric iron Fe3+, but the ideal formula features only ferric iron. It was named in 1928 by Marland P. Billings. The name is for its relationship to hastingsite and its magnesium content. Hastingsite was named for the locality in Dungannon Township, Hastings County, Ontario, Canada.

<span class="mw-page-title-main">Donnayite-(Y)</span> Rare-earth carbonate mineral containing the rare-earth metal yttrium

Donnayite-(Y) is a rare-earth carbonate mineral containing the rare-earth metal yttrium. It was first discovered in 1978 at Mont Saint-Hilaire, Quebec. Donnayite was subsequently identified and named after Joseph D. H. Donnay and his wife, Gabrielle Donnay. Both were prominent mineralogists and crystallographers, and J. D. H. Donnay was awarded the Roebling Award by the Mineralogical Society of America in 1971 for his emphasis on the importance of optical mineralogy and crystal morphology. Donnayite tends to occur in small quantities in the pegmatite dykes and miarolitic cavities of mountainous regions. It crystallizes in this environment with increasing alkalinity values until the alkalinity suddenly drops during the last stage of crystallization. This results in increasing amounts of Na carbonates and REE minerals. First discovered at Mont St-Hilaire, donnayite has since been found in the Southern Ural Mountains of Russia and the Narssarssuk pegmatite of South Greenland. Donnayite crystals tend to be small and the color is commonly pale yellow to yellow with a white streak and a vitreous luster. Donnayite crystals usually display trigonal or hexagonal symmetry and have a hardness of 3. Twinning is extremely common in this mineral. Minerals closely related to donnayite include synchysite, calcite, sphalerite, microcline, and analcime. Donnayite is isomorphous with weloganite and mckelveyite.

<span class="mw-page-title-main">Köttigite</span>

Köttigite is a rare hydrated zinc arsenate which was discovered in 1849 and named by James Dwight Dana in 1850 in honour of Otto Friedrich Köttig (1824–1892), a German chemist from Schneeberg, Saxony, who made the first chemical analysis of the mineral. It has the formula Zn3(AsO4)2·8H2O and it is a dimorph of metaköttigite, which means that the two minerals have the same formula, but a different structure: köttigite is monoclinic and metaköttigite is triclinic. There are several minerals with similar formulae but with other cations in place of the zinc. Iron forms parasymplesite Fe2+3(AsO4)2·8H2O; cobalt forms the distinctively coloured pinkish purple mineral erythrite Co3(AsO4)2·8H2O and nickel forms annabergite Ni3(AsO4)2·8H2O. Köttigite forms series with all three of these minerals and they are all members of the vivianite group.

<span class="mw-page-title-main">Carminite</span> Anhydrous arsenate mineral containing hydroxyl

Carminite (PbFe3+2(AsO4)2(OH)2) is an anhydrous arsenate mineral containing hydroxyl. It is a rare secondary mineral that is structurally related to palermoite (Li2SrAl4(PO4)4(OH)4). Sewardite (CaFe3+2(AsO4)2(OH)2) is an analogue of carminite, with calcium in sewardite in place of the lead in carminite. Mawbyite is a dimorph (same formula, different structure) of carminite; mawbyite is monoclinic and carminite is orthorhombic. It has a molar mass of 639.87 g. It was discovered in 1850 and named for the characteristic carmine colour.

<span class="mw-page-title-main">Talmessite</span>

Talmessite is a hydrated calcium magnesium arsenate, often with significant amounts of cobalt or nickel. It was named in 1960 for the type locality, the Talmessi mine, Anarak district, Iran. It forms a series with β-Roselite, where cobalt replaces some of the magnesium, and with gaitite, where zinc replaces the magnesium. All these minerals are members of the fairfieldite group. Talmessite is dimorphic with wendwilsonite.

Raygrantite is a mineral that was first discovered in Big Horn Mountains, Maricopa County, Arizona, USA. More specifically, it is located in the evening star mine, which is a Cu, V, Pb, Ag, Au, and W mine. Raygrantite is a member of the iranite mineral group, which consists of Hemihedrite, Iranite, and Raygrantite. This mineral received its name in honor of Dr. Raymond W. Grant, a retired professor who primarily focused on the minerals of Arizona. The typical crystal structure of this mineral is bladed with parallel striations to the C axis. It's ideal chemical formula is Pb10Zn(SO4)6(SiO4)2(OH)2. Finally, the IMA (International Mineralogical Association) approved this mineral in 2013, and the first publication regarding this mineral was put forth in 2017.

References

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  8. De Villiers, Johan P R (1971) Crystal Structures of Aragonite, Strontianite and Witherite. The American Mineralogist 56:758
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  11. The Mineralogical Record (2010) 41-1:62 supplement
  12. The Mineralogical Record (2004) 35-4:355
  13. The Mineralogical Record (2004) 35-2:176
  14. The Mineralogical Record 35-4:347 (2004)
  15. Rocks & Minerals (2010) 85-3:212
  16. Rocks & Minerals (2009) 84-4:332

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