Thomsonite

Thomsonite

Thomsonite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, thomsonite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named thomsonite-Ca and thomsonite-Sr. Thomsonite-Ca, by far the more common of the two is a hydrous sodium, calcium and aluminium silicate, NaCa2Al5Si5O20·6H2O. Strontium can substitute for the calcium and the appropriate species name depends on the dominant element. The species are visually indistinguishable and the series name thomsonite is used whenever testing has not been performed. Globally, thomsonite is one of the rarer zeolites.

Thomsonite was first identified in material from Scotland in 1820. It is named for the Scottish chemist Thomas Thomson. The crystal system of thomsonite is orthorhombic. The Mohs hardness is 5 to 5.5. It is transparent to translucent and has a density of 2.3 to 2.4. It may be colorless, white, beige, or somewhat green, yellow, or red. The crystals tend to be long thin blades that typically form radial aggregates, and sometimes fans and tufts. The aggregates are variable and may be spikey in appearance, dense and ball-like, or form worm-like growths. Tight acicular radiating clusters and sphericules are common forms.

Thomsonite occurs with other zeolites in the amygdaloidal cavities of basaltic volcanic rocks, and occasionally in granitic pegmatites. Good examples have been found in Faroe Islands (var. Faroelite [ [http://mimsy.bham.ac.uk/detail.php?t=objects&type=browse&f=id_number&s=BIRUG+785&record=0 The Barber Institute of Fine Arts, the Lapworth Museum of Geology and the University of Birmingham Collections - Objects ] ] ), Scotland, Colorado, New Jersey, Oregon, Nova Scotia, India, and Russia.

Nodules of massive thomsonite that display an attractive banded coloring are found along the shore of Lake Superior. Most of these thomsonite nodules and their derived pebbles are less than 0.6 cm (1/4 inch). Those enclosed in basalt are extremely difficult to remove without breaking them. Consequently, a very large percentage of those used as gemstones have been, and continue to be, pebbles collected from beaches. These days, many are recovered off-shore by scuba divers.

References

* [http://www.mindat.org/min-3941.html Mindat Thomsonite-Ca]
* [http://webmineral.com/data/Thomsonite-Ca.shtml Webmineral Thomsonite-Ca]
* [http://www.minsocam.org/MSA/IMA/ima98(13).pdf IMA Zeolite Classification]
* [http://www.cst.cmich.edu/users/dietr1rv/thomsonite.htm R. V. Dietrich, Thomsonite]


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  • Thomsonite — Thom son*ite, n. [From R. D. Thomson, of Glasgow.] (Min.) A zeolitic mineral, occurring generally in masses of a radiated structure. It is a hydrous silicate of aluminia, lime, and soda. Called also {mesole}, and {comptonite}. [1913 Webster] …   The Collaborative International Dictionary of English

  • thomsonite — ● thomsonite nom féminin (de T. Thomson, nom propre) Aluminosilicate naturel hydraté de calcium et de sodium de la famille des zéolites …   Encyclopédie Universelle

  • thomsonite — tomsonitas statusas T sritis chemija apibrėžtis Mineralas. formulė Na,Ca₂[Al₅Si₅O₂₀]·6H₂O atitikmenys: angl. thomsonite rus. томсонит …   Chemijos terminų aiškinamasis žodynas

  • thomsonite —       rare mineral in the zeolite family, similar to natrolite (q.v.). * * * …   Universalium

  • thomsonite — noun Another name for ozarkite, a mineral native to the United States …   Wiktionary

  • thomsonite — (entrée créée par le supplément) (tom so ni t ) s. f. Terme de minéralogie. Espèce de zéolite …   Dictionnaire de la Langue Française d'Émile Littré

  • thomsonite — thom·son·ite …   English syllables

  • thomsonite — ˈtäm(p)səˌnīt noun ( s) Etymology: Thomas Thomson died 1852 Scottish chemist + English ite : a mineral NaCa2Al5Si5O20.6H2O of the zeolite family consisting of a hydrous silicate of aluminum, calcium, and sodium, occurring generally in masses of a …   Useful english dictionary

  • comptonite — Thomsonite Thom son*ite, n. [From R. D. Thomson, of Glasgow.] (Min.) A zeolitic mineral, occurring generally in masses of a radiated structure. It is a hydrous silicate of aluminia, lime, and soda. Called also {mesole}, and {comptonite}. [1913… …   The Collaborative International Dictionary of English

  • mesole — Thomsonite Thom son*ite, n. [From R. D. Thomson, of Glasgow.] (Min.) A zeolitic mineral, occurring generally in masses of a radiated structure. It is a hydrous silicate of aluminia, lime, and soda. Called also {mesole}, and {comptonite}. [1913… …   The Collaborative International Dictionary of English

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