month's article features a local favorite to our club: Strontianite. Our President,
Hendershot and I have collaborated to bring you a new mix of facts and a geological story.
you ready for our brief visit with Strontianite? Let's go!
embark on a study session, as fieldtrip season is at a close for our club's area.
Let's "bone up" on our strontium minerals a bit, so that we may be prepared in
2006 to collect again. Please join us at the table. Here, I'll pass you each a
study guide to
get started. You begin, while I rustle us up some refreshments.
Aragonite pseudo-hexagonal crystals on a creamy matrix of Strontianite crystals,
Argriento, Sicily, Italy
Strontianite is named after its discovery locality in Strontian, Argkyllshire, Scotland.
Chemical Name and Formula: Strontium Carbonate, SrCO3
Color: Generally colorless to white but is also found in pink, grey and green.
Luster: Vitreous to greasy
Transparency: Transparent to Translucent with a glassy luster
Crystal System: Orthorhombic
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
Cleavage is notable in one direction and poor in another,
Fracture is subconchoidal to uneven
Hardness: 3.5 4 (Copper Penny)
Specific Gravity: 3.7+, (above average for transparent minerals)
Solvency: effervesces in only warm HCl solutions or when powdered in cold HCl.
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
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:
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.
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 winters 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.
fluoresces a weak white both under Longwave (LW) and Shortwave (SW) ultraviolet
light. Sometimes a pale blue or blue-green color can be exhibited.
in Pennsylvania (now closed to collecting) has been a good source of twinned golden
calcite crystals and spherical, white Strontianite clusters. Meckleys 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 Meckleys
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.
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 clubs
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
Much of the
worlds 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 earths
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
We hope that you
have enjoyed our brief coverage on the identification and geology of our favored strontium
mineral this month.
I would like to gratefully acknowledge the generous
contributions of our fellow Strontianite
collectors, authors, curators, professionals, and club members who made this
work possible. Thanks.
Ken is current webmaster of the Delaware
Mineralogical Society.He has a diploma in
Jewelry Repair, Fabrication & Stonesetting from the Bowman Technical School,
Lancaster, PA, and worked as jeweler.He has
also studied geology at the University of Delaware.And,
he is currently a member of the Delaware Mineralogical Society and the Franklin-Ogdensburg
Mineralogical Society. E-mail: email@example.com.
Invitation to Members
Want to see your name in print? Want to co-author, contribute,
or author a whole Mineral of the Month
article? Well, this the forum for you!
And Members, if you have pictures, or a story you would like to
share, please feel free to offer. We'd like to post them for our mutual enjoyment.
Of course, you get full photo and author credit, and a chance to reach other
collectors, hobbyists, and scientists. We only ask that you check your facts, give
credit where it is due, keep it wholesome for our Junior Members watching, and keep on
topic regarding rockhounding.
You don't even have to be experienced in making a webpage. We
can work together to publish your story. A handwritten short story with a Polaroid
will do. If you do fancier, a text document with a digital photo will suit, as well.
Sharing is the groundwork from which we can get your story out there.
Our club's webpages can reach any person surfing the net in the
world, and even on the International Space Station, if they have a mind to view our
We are hoping for a possible tie-in to other informative programs
upon which our fellow members might want to collaborate. Contact any officer or
board member with your suggestions.
Our next MOTM will
be a surprise. For 2005-6, we are waiting for your suggestions. What mineral
do you want to know more about?
Most of the Mineral of the Month
selections have come from most recent club fieldtrips and March Show Themes, and from
inspriring world locales. thus far. If you have a suggestion for a future Mineral of the Month, please e-mail me
at: firstname.lastname@example.org, or tell me at our next meeting.