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Cymrite
Current inventory: 0 gems
 

Cymrite

  
Cymrite is named from Cymru, the Welsh name for Wales, the locality of its discovery. The word Cymru is descended from the Brythonic word combrogi, meaning fellow-countrymen. Old Brythonic was an ancient Celtic language spoken in Britain.

Discovered in 1949; IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

BaAl2Si2(O,OH)8 H2O

 

Hydrated Barium Aluminum Silicate Hydroxide

Molecular Weight:

393.47 gm

Composition:

Barium

34.90 %

Ba

38.97 %

BaO

 

Aluminum

13.71 %

Al

25.91 %

Al2O3

 

Silicon

14.28 %

Si

30.54 %

SiO2

 

Hydrogen

0.51 %

H

4.58 %

H2O

 

Oxygen

36.60 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.38-60

Nickel-Strunz 10th Ed. ID:

9.EG.05

 

9 : SILICATES (Germanates)
E : Phyllosilicates
G : Double nets with 6-membered and larger rings

Related to:

None

Varieties:

None

Synonyms:

ICSD 39400, PDF 17-507

 

 

Crystal Data

   

   

Crystallography:

Monoclinic - Sphenoidal

Crystal Habit:

As thin pseudohexagonal platelets and prisms, to 7 mm; also fibrous. 

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

Perfect on {001}, imperfect on {110}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

2.0 - 3.0

Density:

3.413 (g/cm3)

Luminescence:

Fluorescent; greenish white fluorescence under UV

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Colorless when pure; commonly dark green or brown due to inclusions of alteration products

Transparency:

Translucent

Luster:

Vitreous to silky

Refractive Index:

1.611 - 1.621  Biaxial ( - ), pseudouniaxial

Birefringence:

0.010

Dispersion:

Relatively strong

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

In veinlets cutting hydrothermal manganese silicate ore (Benallt mine, Wales); in a copper-bearing deposit in dolostones and siderites (Ruby Creek, Alaska, USA); in jadeite graywacke near the contact of an ultramafic rock and the Franciscan Formation (San Benito County, California, USA); a product of high-pressure metamorphism of manganese-rich rocks (Andros Island, Greece).

Common Associations:

Ganophyllite (Benallt mine, Wales); Calcite, Albite, Lawsonite (San Benito County, California, USA); Hyalotekite, Banalsite, Hyalophane, Hedyphane, Manganoan Biotite (Långban, Sweden).

Common Impurities:

Fe, Mn, K

Type Locality:

Benallt Mine (Tyddyn Meirion mine; Ty Canol mine), Rhiw, Llanfaelrhys, Lleyn Peninsula, Gwynedd, Wales, UK

Year Discovered:

1949

View mineral photos:

Cymrite Mineral Photos and Locations

 

 

Unusual Gem Categories

   

   

 

Fluorescent Gems

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Cymrite is a rare barium silicate mineral that is roughly equivalent to hydrated Celsian and forms in barium-rich rocks under conditions of low grade metamorphism. Cymrite was first described from material collected in 1944 by Dr. A.W. Groves and Dr. W. Campbell Smith at the Benallt manganese mine, near Rhiw, Llanfaelrhys, Lleyn Peninsula, Gwynedd, Wales, UK. Cymrite is colorless when pure but commonly dark green or light to dark brown due to impurities. It is translucent with vitreous to pearly luster and a Moh's hardness of 2-3. Cymrite may show greenish white fluorescence under UV light.

Cymrite is named from Cymru (pronounced kumry), the Welsh name for Wales, the locality of its discovery. The word Cymru is descended from the Old Brythonic word combrogi, meaning fellow-countrymen. Old Brythonic was an ancient Celtic language spoken in Britain.

Cymrite distribution: in the Benallt mine, Rhiw, Lleyn Peninsula, Wales. From Långban, Värmland, Sweden. In the USA, from Ruby Creek, Brooks Range, Alaska, and near Pacheco Pass, San Benito County, California. On Andros Island, Cyclades Islands, Greece. From the Lianyuan-Shaoyang area, Hunan Province, China. In the Shiramaru mine, Tokyo Prefecture, Japan. At Northwest Nelson, South Island, New Zealand. In the Saureisk deposit, Polar Ural Mountains, and near Lake Baikal, eastern Siberia, Russia. From the Black Rock and Hotazel mines, near Kuruman, Cape Province, South Africa. At Kalugeri Hill, Babuna River, Jakupica Mnts, 15 km NW of Nežilovo, Veles, Republic of Macedonia. A number of other occurrences are known.
 

  
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