Strontianite Basics by Karissa Hendershot      Strontianite is named after its discovery locality in Strontian, Argkyllshire, Scotland. PHYSICAL CHARACTERISTICS: 1.                Chemical Name and Formula: Strontium Carbonate, SrCO3 2.                Class: Carbonate 3.                Color: Generally colorless to white but is also found in pink, grey and green. 4.                Luster: Vitreous to greasy 5.                Transparency: Transparent to Translucent with a glassy luster 6.                Crystal System: Orthorhombic 7.                Crystal Habits include compact, granular, concretionary and massive forms. Crystals are uncommon and are usually pointed and nearly acicular in radiating clusters or tufts. Also forms a pseudo-hexagonal trilling twin is similar to, but is far rarer than aragonite's famous twin. 8.                Cleavage is notable in one direction and poor in another, 9.                Fracture is subconchoidal to uneven 10.            Hardness: 3.5 – 4 (Copper Penny) 11.            Specific Gravity: 3.7+, (above average for transparent minerals) 12.            Streak: White 13.            Solvency: effervesces in only warm HCl solutions or when powdered in cold HCl. 14.            Associated Minerals include: Magnesite, Calcite, Celestite 15.            Ultraviolet: fluoresces bright blue-white under UV illumination 16.            Best Field Indicators are crystal habits, reaction to acid and density        Notable Occurrences include: Strontian, Scotland; San Bernito Co, California and Cave-in-rock, Illinois, USA; Austria and Germany and of course Meckley Quarry in Bedford, Pennsylvania        The element Strontium is found predominately in two minerals, strontium sulfate (SrCO4), known as Celestite and strontium carbonate (SrCO3), know as Strontianite.

 

 

     Strontianite is found in low-temperature hydrothermal veins associated with calcite, celestite and sulfides such as found at Meckley Quarry in Bedford, Pennsylvania.

     It was mined for a while in Germany for strontium, an element used as a coloring agent of fireworks and other applications.

     Strontium is a metallic element that commonly occurs in nature; only two minerals, Celestite (strontium sulfate) and Strontianite (strontium carbonate), however, contain Strontium in sufficient quantities to make its recovery practical. Crystals are rarer than the massive forms, and so are usually sold as specimens. Typical specimens have spiky, minute crystals in radiating aggregates or tufts. However, it also forms pseudohexagonal twins similar to aragonite's famous twin. Of the two, Celestite occurs much more frequently in sedimentary deposits of sufficient size to make mining attractive.

 

COMMERCIAL USES FOR STRONTIANITE:

     Strontium ores for commercial use have not been mined in the United States since 1959. The world's largest producers are, in descending order of output, Mexico, Spain, and China. The United States imports its commercial Celestite from Mexico. It is processed into a variety of strontium chemicals that are used mainly in the faceplate glass of color television picture tubes. Strontianite is also used in fireworks to create the deep red colors, and in the sugar beat industry.

References:

1. Simon & Schuster’s Guide to Rocks and Minerals
2. www.Mindat.org
3. http://www.theimage.com/mineral/strontianite/index.htm
4. http://mineralgalleries.com
5. Strontium by Joyce A. Ober
6. www.Speclab.com
7. http://resourcescommittee.house.gov/subcommittees/emr/usgsweb/materials

 

Strontianite Geology
by Ken Casey

     Though a rare mineral, Strontianite can capture our imagination, if we choose to delve into its ice-like crystal forms.  Like a miniature snowscape, our MOTM resembles ice, but does not crystallize in its forms.  Supported by its vuggy matrix, white ball-like clusters cap the edges of open spaces to create a mock arsenal of snowballs for a fictional small scale snowball fight amongst children on a bright winter’s day in extreme northern or southern climes.  A model railroader might consider using his or her specimens to crown a train layout.

     As a thumbnail or larger mineral specimen in your collection, you can appreciate your Strontianite in at least two other ways: in daylight, or under fluorescent light.

     In daylight, it can almost glow a bright white in its druzy or snowball-shaped forms.  Its nearly transparent, acicular crystals can also impart this glow.

     Strontianite fluoresces a weak white both under Longwave (LW) and Shortwave (SW) ultraviolet light.  Sometimes a pale blue or blue-green color can be exhibited.

     Winfield Quarry in Pennsylvania (now closed to collecting) has been a good source of twinned golden calcite crystals and spherical, white Strontianite clusters.  Meckley’s Quarry in Mandata, PA also offers similar strontium carbonate crystals, but with clear blue Celestite (strontium sulfate).  These rare fibrous crystals can appear to resemble snow and tiny snowballs.  The matrix is vuggy limestone in both of these southeastern Pennsylvania locales.  This author has a few specimens from one of Meckley’s generous open houses.  But, like some of us in the hobby, have so much in our collections over the years, cannot find one to photograph for this article.  I will, however offer to links of some folks who have had greater success therein.

     Many such limestone beds around the world are chemically suited to be used as a raw material in either concrete blocks or hydraulic cement.  Typically, such minerals as calcite, aragonite, Strontianite, celestite, and epsomite, pyrite, and fluorite accompany Strontianite in similar assemblages forming in limestone cavities.  Our club’s fieldtrip area encompasses many of these sites.  Quartz in magnesium dolomites is also a possibility.  Hydrothermal veins, however, can deposit more metallic ore minerals, like galena and sphalerite.  Even gypsum (a sulfate) and chalk (a limestone) have been associated with Strontianite in certain North American and European geologic environments.

     Much of the world’s karst topographies could yield strontium-based minerals.  Ancient sedimentary seabeds metamorphosed over time into dolostone.  In his book, Oxygen : The Molecule that Made the World , Nick Lane relates many of the earth’s geologic processes and depositions to organic processes.  One theory of formation suggests deep marine deposition of strontium derived in part from earlier life. 

     Some studies have been done comparing the Sr87:Sr86 isotopes.  By comparing the ratios of these radiogenic sediments, we can ascertain a proposed age of the earth, or even radiometrically date geologic strata, hence key into the geologic paleoenvironments that formed them. 

     They may also be used as key isotopic indicators in petrology, specifically in diamond-mining.  So, strontium is important in geologic research.  Perhaps there are some hidden new theories we could derive from a further study of concentrated Strontianite deposits.

     As a note of caution to our proposed studies, you might want to be mindful that pure metallic strontium can be toxic to humans, as it prefers to replace calcium in teeth and bones.  In fact, bone marrow cancer is one likely scenario.  Professional scientists are trained to handle it in its elemental form.  As we are concerned only with more stable minerals forms, we are working a greatly safer compound.  Of course, these minerals, though resembling edible salts, are not to be consumed, unlike halite salts.  So, please, do not use the “taste test” to aid in identifying this salient mineral.  Your safety is of paramount importance to us.

     As our planet supports life, especially that of mineral enthusiasts like yourself, you may wish to study up on Strontianite, and how it can help you to better understand our universe.  Perhaps you may desire to travel to a famous collecting site, or even visit a local rock & mineral show to swap or purchase specimens for yourself, or to share with others. 

     We hope that you have enjoyed our brief coverage on the identification and geology of our favored strontium mineral this month.