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Thaumasite
Current inventory:  1 gem
 

Thaumasite

Chemistry:  Ca3Si(CO3)(SO4)(OH)6·12(H2O)

Discovered in 1878;   IMA status: Valid (pre-IMA; Grandfathered).
Thaumasite is named from the Greek word thaumazein meaning surprising in allusion to its rather unusual chemical composition with carbonate, sulphate and hexahydroxysilicate anions.

 

Classification

   

   

Mineral Classification:

Sulfates

Strunz 8th Ed. ID:

8/B.22-90

Nickel-Strunz 10th Ed. ID:

7.DG.15

 

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H
2O
G : With large and medium-sized cations; with NO
3, CO3, B(OH)4, SiO4 or IO3
15 : Ettringite Group

 

 

Crystal Data

   

   

Crystallography:

Hexagonal - Dipyramidal

Crystal Habit:

Crystals prismatic, to 5 cm; typically acicular, radiating; powdery, compact, massive.

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

Poor, Indistinct

Fracture:

Subconchoidal

Tenacity:

Brittle

Moh's Hardness:

3.5

Density:

1.88 - 1.90 (g/cm3)

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Colorless, white, pale yellow.

Transparency:

Transparent to Translucent

Luster:

Vitreous, Silky, Greasy

Refractive Index:

1.458 - 1.507  Uniaxial ( - )

Birefringence:

0.0390

Dispersion:

Very Weak to None

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

A very late-stage mineral in some sulfide ore deposits. In contact metamorphic zones and from the reaction of geothermal waters or seawaters with basalts and tuffs.

Type Locality:

Bjelke Mine, Åreskutan, Åre, Jämtland, Sweden

Year Discovered:

1878

View mineral photos:

Thaumasite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Thaumasite
is an extremely rare gem and a member of the Ettingite Group of minerals that includes Charlesite, Ettringite, Sturmanite and Thaumasite. It was discovered at the Bjelke Mine, Åreskutan, Åre, Jämtland, Sweden in 1878. It is a soft mineral but seems to harden with exposure to air. Sources of gem quality crystals include Paterson, New Jersey and the Kalahari manganese fields of the Northern Cape Province, South Africa.
 

  
Thaumasite gems for sale:

Thaumasite-001A

Gem:

Thaumasite

Stock #:

THAU-001

Weight:

0.220 ct

Size:

5.0 x 3.61 x 2.53 mm

Shape:

Cut corner rectangle

Color:

Colorless

Clarity:

Eye clean - VS2

Origin:

N'Chwaning mine, South Africa

Treatment:

None (natural)

Price:

$220.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Thaumasite-001B

This extemely rare gem is from the N'Chwaning Mine in South Africa. It is mostly eye clean, with just a couple hard to see inclusions, and very bright.


 

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