Strontianite (SrCO<sub>3</sub>) 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:
Strontium is never found free in nature. The principal strontium ores are celestine SrSO<sub>4</sub> and strontianite SrCO<sub>3</sub>. The main commercial process for strontium metal production is reduction of strontium oxide with aluminium. When the CO<sub>3</sub> 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 CO<sub>3</sub> groups lie perpendicular to the c axis, in two structural planes, with the CO<sub>3</sub> triangular groups of one plane pointing in opposite directions to those of the other.
Crystal form
Strontianite occurs in several different habits. Crystals are short prismatic parallel to the c axis and often acicular.
The maximum birefringence δ is 0.15 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.
Canada
The Francon quarry, Montréal, Québec. <br />
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.
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. 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.
United States
In the Gulf coast of Louisiana and Texas, strontianite occurs with celestine in calcite cap rock of salt domes.
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.
In Schoharie County, New York, it occurs in geodes and veins with celestine and calcite in limestone,