strontianite

n.
A gray to yellowish-green ore of strontium, SrCO₃.

[strontian, strontianite (short for Strontian earth, after Strontian, a village of west-central Scotland) + -ITE¹.]

The mineral form of strontium carbonate, usually with some calcium replacing strontium. It characteristically occurs in veins with barite or celestite or as masses in certain sedimentary rocks. Strontianite is normally prismatic, but it may also be massive. It may be colorless or gray with yellow, green, or brownish tints. The hardness is 3^½ on Mohs scale, and the specific gravity of 3.76. It occurs at Strontian, Scotland, and in Germany, Austria, Mexico, and India and, in the United States, in the Strontium Hills of Calfornia. See also Carbonate minerals; Strontium.

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SrCO
Orthorhombic -- Rhombic bipyramidal

Environment

Veins or concretions in sedimentary rocks.

Crystal description

Most common formation is in fibrous veinlets. Also in acicular crystals (long needles), massive, and fine-grained; pseudohexagonal trillings are the rarest of the aragonite group.

Physical properties

White or colorless, light green, pink, yellowish, brownish, or gray. Luster glassy; hardness 3Ɖ-4; specific gravity 3.7; fracture uneven; cleavage 1 good and 1 poor. Brittle; transparent to translucent.

Composition

Strontium carbonate (70.1% SrO, 29.9% CO ₂ ) sometimes with a little Ca.

Tests

Like witherite, readily soluble in warm acid; the concentrated solution forms slender, white, water-soluble crystals on cooling. Precipitates strontium sulfate crystals when sulfuric acid is added to solutions of medium strength. Strong hydrochloric acid solution gives a brilliant red flash (strontium flame) when a platinum wire dipped in it is thrust into the Bunsen burner flame.

Distinguishing characteristics

Recognized as a carbonate by ease of solution in hydrochloric acid with the release of bubbles and by softness, and as a strontium mineral by the brilliant red flame color.

Occurrence

Strontianite locally was an important source of strontium used in the refining of sugar and in making fireworks. It was mined only in Germany at Drensteinfurt, near Hamm, where veins cut shaley limestone beds underlying beet fields.

The narrow veins, up to several inches across, contained frequent crystal-lined cavities. They were the source of the best-known specimens but are now only of historical interest. Also found in fibrous veins in Germany, England, and the U.S. Sometimes forms nodules in limestone, as at Schoharie, New York, in Pennsylvania, and near Barstow, California. Long, pale pink, loosely aggregated needles and compact masses have been found near Cave-in-Rock, Illinois, associated with fluorite and witherite. Brown-tipped, pencil-thick elongated 1-in. (2 cm) trillings found in Oberndorf, Styria, Austria, are the best recently available specimens.

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