The Mineral Thomsonite

Thomsonite Mineral

A tectosilicate type chain mineral from the zeolite group, is known as Thomsonite, which, before 1997, was documented as a type of mineral, but the IMA or the International Mineralogical Association made an amendment and brought it under the series category during 1997 and these varieties of minerals we named as Thomsonite-Sr and Thomsonite-Ca, where the former, with dominating strontium, is called thomsonite-Sr, which is very rare. Nearly all collectors possessing specimen of Thomsonite have only Thomsonite-Ca with them

Chemical Formula

NaCa 2 Al 5 Si 5 O 20 ·6H 2 O

Derivation of Name

It was Henry James Brooke in 1820 who renamed it to honor of a well known Scottish professor of chemistry in the University of Glasgow, a mineral enthusiast. Thomsonite has orthorhombic crystals.

Occurrence

Thomsonite is found in the company of other zeolites in the cavities of volcanic basaltic rocks, and intermittently with pegmatites of granite.

Gemology

An appealing tendency of Thomsonite is to appear as round, concentric, polished bands of stones that have good aesthetic looks. This exterior is most often found at Thomsonite Beach at Grand Marais, Minnesota, on the shoreline of Lake Superior. It generally appears along with other zeolites plus green Chlorite.

Source

Specimens have been located in the Faroe Islands, Oregon, New Jersey, India, Nova Scotia and Russia.

Mineralogy

Thomsonite is a rare and sought-after member of the group zeolite, appearing in inimitable and exciting crystal aggregates. During1997, the Zeolite Subcommittee of the IMA divided the mineral into two separate sub-species and started considering Thomsonite as a sequence of two materials. The sequence is made distinct by including strontium and calcium as end members. Ordinary thomsonite that is calcium-dominated is known as Thomsonite-C. It’s generally pure and devoid of any strontium.

Color

It can be white, colorless, beige, or green, red or yellow to some extent. It can occur as clear or translucent

Density 

2.366 g/cm 3

The Mohs hardness

5 to 5.5.

Density

2.3 to 2.4.
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