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Strontianite
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Strontianite
Strontianite from Slovakia
General
CategoryCarbonate minerals
FormulaSrCO3
IMA symbolStr[1]
Strunz classification5.AB.15 (10 ed)
5/B.04-20 (8 ed)
Dana classification14.01.03.03
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPmcn
Unit cella = 5.1 Å, b = 8.4 Å
c = 6.0 Å; Z = 4
Identification
Formula mass147.63 g/mol
ColorColourless, white, gray, light yellow, green or brown; colourless in transmitted light
Crystal habitPrismatic, acicular, pseudo hexagonal, columnar to fibrous, granular, massive
TwinningVery common, usually contact, rarely penetration, also repeated
Cleavage{110} nearly perfect, {021} poor, {010} traces
FractureSubconchoidal to uneven
TenacityBrittle
Mohs scale hardness3+1⁄2
LustreVitreous, resinous on breaks, greasy
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity3.74 to 3.78 Transparent versions are heavier than the other ones
Optical propertiesBiaxial (−)
Refractive indexnα = 1.52, nβ = 1.66, nγ = 1.67
Birefringence0.15
2V angleMeasured: 7°, Calculated: 12° to 8°
Ultraviolet fluorescenceAlmost always fluorescent
SolubilitySoluble in dilute HCl
Alters toCelestine SrSO4
References[2][3][4][5]

Strontianite (SrCO3) 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.

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

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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

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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

[edit]

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]

Radial aggregate of strontianite
Acicular strontianite in spherical aggregates
Strontianite in pseudo-hexagonal crystals

Optical properties

[edit]

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:

  • nα = 1.520, nβ = 1.667, nγ = 1.669[2]
  • nα = 1.516 – 1.520, nβ = 1.664 – 1.667, nγ = 1.666 – 1.668[3][4]
  • nα = 1.517, nβ = 1.663, nγ = 1.667 (synthetic material)[9]

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

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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

[edit]

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+1⁄2,[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

[edit]

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

[edit]

Type locality

[edit]

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

[edit]

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

[edit]

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

India

[edit]

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

Mexico

[edit]

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

Russia

[edit]

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

[edit]

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]

  • Strontianite from Strontian, Scotland
    Strontianite from Strontian, Scotland
  • Dresserite and Strontianite from the Francon quarry, Canada
    Dresserite and Strontianite from the Francon quarry, Canada
  • Strontianite from the Dreislar Mine, North Rhine-Westphalia, Germany
    Strontianite from the Dreislar Mine, North Rhine-Westphalia, Germany
  • Strontianite from Texas, US
    Strontianite from Texas, US
  • Strontianite from Illinois, US
    Strontianite from Illinois, US
  • Strontianite from California
    Strontianite from California

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Strontianite

View on Grokipedia
from Grokipedia
Strontianite is a rare with the SrCO₃, consisting primarily of , and it belongs to the group with an . It typically exhibits a vitreous to resinous luster, a Mohs of 3.5, and a specific ranging from 3.74 to 3.78, appearing in colors such as colorless, white, gray, light yellow, green, or brown, often with fluorescence under ultraviolet light. The mineral displays very good prismatic cleavage and is brittle, soluble in dilute , making it distinguishable from similar carbonates like or . Discovered in lead mines near the village of in , , during operations that began in 1722, strontianite was first described and named in 1791 by German scientist Friedrich Gabriel Sulzer after its type locality. The mineral played a key role in the identification of the element , as chemists Adair Crawford and William Cruikshank analyzed samples in the 1780s and published findings in 1790, with Sir later isolating the pure element in 1808. Strontianite forms primarily in low-temperature hydrothermal veins, as a mineral in deposits, or through metasomatic replacement in , , or . It is one of the two principal ores of , alongside celestine (SrSO₄), though less commonly mined due to its rarity; derived from strontianite is used in producing for applications including (for red flames in ), sugar refining from beet , purification, and glazes.

Nomenclature and History

Etymology

Strontianite derives its name from the village of in Argyllshire, , the site of its initial discovery in a lead mine. The village's name stems from the phrase Sròn an t-Sìthein, translating to "nose of the hill" or "point of the hill," which describes a prominent knoll or rounded hill in the local landscape traditionally associated with the mythological sìdhe, or , in Highland . This highlights the cultural and geographical ties of the naming, as sròn refers to a nose-like projection or , and sìthein denotes a fairy dwelling or enchanted mound. In line with mineralogical conventions of honoring type localities—the original sites of discovery—the name "strontianite" was formalized in 1791 by German mineralogist Friedrich Gabriel Sulzer. The element , the primary component of strontianite, shares this naming origin from the same Scottish village.

Discovery

Strontianite was first encountered around 1787 by local miners working lead deposits in the hills near the village of in Argyllshire, , where it appeared as an unusual white, earthy associated with the . Samples of this material were collected and sent to for scientific examination, initially mistaken for a variety of barytes or . In 1790, Irish physician and chemist Adair Crawford and William Cruikshank, working with samples from these mines, conducted detailed chemical analyses that revealed the mineral's distinct properties, including differences in solubility and reaction behaviors compared to (). Crawford's experiments led him to conclude that the substance contained a new "earth" or alkaline base, which he termed strontia, thereby identifying the element as previously unknown. His findings were published in a seminal that year, marking the initial scientific recognition of this novel material. The mineral received its formal description and name, strontianite, in 1791 from German mineralogist Friedrich Gabriel Sulzer, honoring its type locality at —the etymological root of both the mineral and element names. Scottish independently verified Crawford's observations through further experiments in 1791–1792, confirming strontianite as a distinct species by demonstrating its unique coloration (a crimson red) and other diagnostic traits that set it apart from calcium and compounds. Early 19th-century investigations, building on Hope's work, solidified the understanding of strontianite's composition as a , with analyses emphasizing its structural similarity to other alkaline earth while highlighting the role of . These studies, including those by prominent chemists of the era, established its identity beyond initial doubts and paved the way for broader mineralogical classification.

Chemical and Structural Properties

Composition

Strontianite is a with the SrCO₃, serving as one of the principal natural sources of alongside celestite. Its is 147.63 g/mol, reflecting the combination of (59.35% by weight), carbon (8.14%), and oxygen (32.51%). In its ideal end-member composition, strontianite consists of approximately 70% SrO and 30% CO₂ by weight, providing a stoichiometric basis for its role in strontium extraction processes. Natural occurrences of strontianite often feature minor substitutions where calcium (Ca) replaces strontium (Sr) isomorphously, up to approximately 25 mol% as CaCO₃, while barium (Ba) substitutions are possible but typically limited and less prevalent. The pure Sr-dominant end-member remains the defining form, with these substitutions influencing local stability without altering the fundamental carbonate structure. Strontianite belongs to the aragonite group of orthorhombic carbonates, which includes minerals like (CaCO₃) and (BaCO₃), sharing similar structural motifs despite varying cation sizes. This group membership underscores strontianite's crystallographic affinity to other alkaline earth carbonates, facilitating its formation in comparable geological settings.

Crystal Structure

Strontianite exhibits an orthorhombic crystal structure with Pmcn (No. 62). This arrangement places it within the aragonite group, where it is isostructural with (CaCO₃), sharing the same structural framework characterized by alternating layers of cations and carbonate anions. In the lattice, Sr²⁺ ions are coordinated by nine O²⁻ atoms from six distinct CO₃²⁻ groups, forming distorted tricapped trigonal prismatic SrO₉ polyhedra arranged in layers parallel to the (001) plane. These polyhedra share edges to create infinite chains parallel to the c-axis, which are linked laterally by nearly planar CO₃²⁻ groups that alternate in orientation along the b-axis, contributing to the overall stability of the framework.

Unit Cell

Strontianite has an orthorhombic belonging to the Pmcn. The lattice parameters are a = 5.11 , b = 8.42 , and c = 6.03 . There are four units per (Z = 4). The calculated from these parameters is approximately 3.76 g/cm³. Relative to , strontianite's is slightly larger, a consequence of the greater of Sr²⁺ (1.31 in ninefold coordination) versus Ca²⁺ (1.18 ).

Physical and Optical Characteristics

Physical Properties

Strontianite exhibits a Mohs hardness of 3.5, making it relatively soft and susceptible to scratching by common minerals like . Its specific gravity ranges from 3.74 to 3.78, reflecting the density contributed by its content. The mineral displays distinct cleavage on the {110} plane, which is nearly perfect, and imperfect cleavage on the {021} plane, a feature influenced by its orthorhombic symmetry. When cleavage is absent, strontianite shows a subconchoidal to uneven . It occurs in various colors, including white, colorless, gray, pale yellow, green, or brown, often due to trace impurities. The streak is consistently white. Strontianite effervesces weakly in dilute , releasing gas as it dissolves.

Optical Properties

Strontianite exhibits biaxial negative optical character, consistent with its orthorhombic crystal structure. The principal refractive indices are α = 1.517 (X = c), β = 1.663 (Y = b), and γ = 1.667 (Z = a). These values result in a birefringence of δ = 0.150, which is moderate and produces noticeable interference colors in thin sections under polarized light. The mineral shows no pleochroism, appearing colorless in transmitted light regardless of orientation. The 2V , which measures the acute between the optic axes, is measured at approximately 7° and calculated between 8° and 12°, indicating a small axial typical for this . Dispersion is weak, with r < v, meaning the refractive indices vary slightly with but do not significantly affect optical identification.

Luminescence

Strontianite displays primarily through under (UV) excitation, with emissions that are generally weak to moderate in intensity. Under short-wave UV (254 nm), it typically fluoresces white to bluish-white, while long-wave UV (365 nm) can produce similar white or bluish hues, occasionally with rare greenish-white or pink variations observed in certain specimens. These fluorescent properties are nearly ubiquitous but vary by locality and trace impurities, making a diagnostic but not dominant feature of the mineral. Phosphorescence in strontianite is absent or very weak, persisting briefly as a faint greenish glow following short- or long-wave UV exposure in some samples. This afterglow is infrequent and short-lived, rarely exceeding a few seconds. Thermoluminescence occurs in select specimens, manifesting as emissions peaking in the UV-blue (– nm) and (500–800 nm) spectral regions upon heating, with a top thermal limit around °C for UV-blue emissions. This property arises from trapped electrons released by thermal energy and is not consistently observed across all samples. The in strontianite is attributed to trace activators such as Mn²⁺ ions, which facilitate red emissions via electronic transitions, and hydrous molecules or organic inclusions responsible for UV-blue . Rare earth elements like Dy³⁺, Tb³⁺, and Sm³⁺ may contribute to specific emission lines at 480 nm, 540 nm, and 640 nm, respectively, though these are less common. Such effects are most notably documented in specimens from the type locality at , , UK, and other select sites like Winfield, , USA, where environmental conditions during formation enhance activator incorporation.

Geological Context

Formation Environment

Strontianite primarily forms in low-temperature hydrothermal environments within carbonate-rich host rocks such as limestones, marbles, and chalks. These conditions involve the circulation of strontium-bearing fluids through fractures or veins, leading to precipitation of where strontium ions react with dissolved in the presence of . The process often occurs at temperatures ranging from 50 to 200°C, as inferred from experimental simulations of hydrothermal alteration and natural paragenetic assemblages. The associated pressures are low, typical of shallow crustal hydrothermal systems, facilitating near-surface or involvement in fluid circulation. Strontianite is also linked to carbonatization processes around alkaline intrusions, where metasomatic alteration introduces into surrounding rocks, promoting mineralization. Additionally, it develops secondarily through the replacement of primary in altered zones or as infillings in cavities and geodes, where evolving fluids concentrate in settings. The stability of SrCO₃ in these environments is favored by the prevalence of carbonate-rich, mildly alkaline fluids.

Associated Minerals

Strontianite commonly occurs with , , celestine (SrSO₄), barite, and , forming paragenetic associations in low-temperature hydrothermal environments. These minerals often coexist in limestone-hosted deposits, where strontianite may replace through metasomatic processes. In systems, particularly those linked to lead-zinc deposits, strontianite serves as a mineral alongside , , , and other sulfides. Less common associations include alstonite and in settings. Strontianite often develops zonal arrangements, such as porous rims around celestine or pseudomorphic replacement of it, highlighting fluid-mediated transformations. These mineral assemblages signal the involvement of strontium-enriched hydrothermal fluids.

Occurrences

Type Locality

Strontianite's type locality is situated in the Strontian district, approximately 4 km north of the village of in the Highland region of , , at coordinates 56°42′N 5°33′W. This site, encompassing the Strontian Mines (Site of Special Scientific Interest), spans 49.77 hectares and features the Strontian Main Vein, a prominent east-west trending mineralized shear zone up to 15 m wide and at least 300 m deep. The mineral occurs in hydrothermal veins hosted within Dalradian schists and associated limestones, forming part of low-temperature deposits in a complex geological setting influenced by nearby intrusions of the Strontian Complex. At this locality, strontianite typically appears as fibrous or columnar crystals, often white to pale green, and is closely associated with () and (), alongside common minerals such as , , and . These specimens were key to distinguishing strontianite from similar carbonates like during its initial characterization. Historical mining at began in the early , with lead () discovery in 1722 leading to the opening of mines in 1725 and peak production around 1730, when the operations employed up to 600 workers and included a dedicated facility. The lead mines, worked intermittently until the late (with barite extraction resuming briefly in the 1980s), provided the samples first analyzed in by Adair Crawford, who identified the novel content in what became known as strontianite. Today, no active occurs at the site, which was last commercially exploited for in the before closure. The area is protected as an SSSI, notified in 1974 and re-notified in 1987, preserving its mineralogical significance; strontianite remains collectible from spoil heaps, though access is regulated to maintain the 's geological integrity.

Other Notable Localities

In , significant strontianite occurrences include the deposits near Barstow, , , where it forms in vein deposits within low hills, often associated with celestite and . In , , the Poudrette quarry at yields large, prismatic to acicular crystals of strontianite in vugs within alkaline igneous rocks, prized by collectors for their size and transparency. Europe hosts several classic localities for strontianite. In , the Clausthal area in the Mountains features strontianite in hydrothermal veins, typically as fibrous or columnar aggregates with barite and . Italy's region, particularly the Massa-Carrara Province, produces strontianite in marble quarries near , often as radiating clusters in cavities associated with dolomite. In Russia, the , including the Korkodinskoye deposit in the Middle Urals, contain strontianite associated with celestite in carbonatite-related settings and gem-quality . In , strontianite is reported from the Ambadungar carbonatite complex in , , where it occurs in veins as massive to granular forms with . Mexico's Ojuela mine in Mapimí, , features strontianite as white, acicular filling cavities in fluorite-rich geodes. Strontianite at these sites vary from massive aggregates to delicate acicular habits, making them highly sought after for mineral collections.

Economic Importance

Extraction and Production

Strontianite, as a primary mineral, is typically extracted through open-pit or methods when occurring in shallow vein deposits or as replacements in , though underground techniques may be employed for deeper occurrences. Due to its association with unconsolidated sediments in many localities, such as the historical deposits near , open-cut operations predominate to avoid instability in loose clay host rocks. Often, strontianite is recovered as a during celestite ( ) mining in strontium-rich regions, where selective hand-sorting or simple crushing separates the carbonate from materials like . Processing begins with beneficiation via crushing and grinding, followed by flotation or to achieve concentrates exceeding 90% SrCO₃ purity. The is then calcined at temperatures around 1,200–1,400°C to decompose it into (SrO) and , yielding a reactive intermediate for further refinement. For purification, SrO's in acids such as hydrochloric or allows leaching to form soluble strontium salts, from which impurities are removed by or before reconversion to desired compounds like or . Reduction to metallic , though uncommon due to limited demand, involves aluminothermic processes where SrO is reacted with aluminum at high temperatures (above 1,000°C) in a to produce strontium vapor, which is condensed. Global strontium production, predominantly from celestite, reached approximately 340,000 metric tons of ore in 2022, equivalent to about 160,000 metric tons of contained , with major output from , , , and . By 2023, global production had increased to an estimated 520,000 metric tons of ore. Strontianite contributes modestly in strontium-enriched areas of and , where it supplements celestite operations, but its rarity limits overall impact to less than 5% of total supply. Historical mining in the early , such as the 500 tons produced from deposits in 1917, supported wartime needs in the United States, but modern production emphasizes efficient celestite processing over strontianite due to the latter's dispersed, low-grade occurrences. Key challenges include the mineral's and low concentrations in viable deposits, often below 50% SrCO₃, necessitating extensive and higher costs compared to celestite. Environmental concerns arise primarily from acid leaching stages, which generate acidic effluents potentially contaminating with and if not managed through neutralization and . Ongoing efforts focus on closed-loop hydrometallurgical circuits to mitigate these impacts.

Uses of Strontium

Strontium compounds, derived from which may be sourced from strontianite or produced from celestite, play a significant role in , where (Sr(NO₃)₂) is widely used to produce a vivid flame color in , flares, and signaling devices. This application leverages the element's ability to emit bright light when heated, making it essential for visual effects in displays and emergency signals. In electronics, strontium is incorporated into ferrite magnets, such as strontium hexaferrite (SrFe₁₂O₁₉), which are valued for their high coercivity, corrosion resistance, and cost-effectiveness in applications like electric motors, speakers, and generators. Historically, strontium compounds were key components in cathode ray tube (CRT) phosphors and glass to absorb X-rays and enhance color rendering, but their use has sharply declined since the early with the widespread adoption of displays (LCDs). Strontium serves as an alloying additive in , particularly in production where metallic acts as a deoxidizer to remove oxygen impurities and improve castability, and in aluminum alloys to modify microstructure for better mechanical properties and reduced . In , was once prescribed for treating severe in postmenopausal women and men at high risk, as it reduced vertebral incidence by promoting formation and inhibiting resorption. However, due to increased risks of cardiovascular events and other adverse effects, its marketing authorization was withdrawn in the in 2017, leading to its discontinuation in many markets. Environmental and health concerns have prompted regulatory actions on certain strontium compounds, with the (ECHA) proposing harmonized classification for under REACH in 2024, potentially leading to restrictions or phasing out in specific industrial applications.

References

  1. https://www.mindat.org/min-3805.html
  2. https://www.nms.ac.uk/discover-catalogue/the-discovery-of-mineral-strontianite
  3. https://www.minerals.net/mineral/strontianite.aspx
  4. https://pubs.usgs.gov/publication/70186705
  5. https://www.mindat.org/loc-3036.html
  6. https://www.scotsman.com/news/place-name-of-the-week-strontian-sra2n-an-t-sathein-1463757
  7. https://www.livescience.com/34522-strontium.html
  8. https://periodic-table.rsc.org/element/38/strontium
  9. https://www.webelements.com/strontium/history.html
  10. https://www.nature.com/articles/nchem.2376
  11. https://sites.chemistry.unt.edu/~jimm/rediscovery%207-09-2018/Hexagon%20Articles/strontium.pdf
  12. https://pubs.usgs.gov/bul/0660i/report.pdf
  13. https://pubchem.ncbi.nlm.nih.gov/compound/Strontium-carbonate
  14. https://msaweb.org/AmMin/AM61/AM61_1001.pdf
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