Cymrite
Current inventory: 0 gems
 

  
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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