Cymrite
Chemical formula: Ba(Si,Al)<sub>4</sub>(O,OH)<sub>8</sub>·H<sub>2</sub>O
Cymrite is a rare barium aluminum silicate, forming colorless or white, hexagonal crystals with a pearly luster.
Properties
- Mohs hardness
- 2-3
- Luster
- Pearly, Dull
- Streak
- White
- Density
- 3.43
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Translucent to Opaque
- Crystal system
- Hexagonal
Diagnostic features
## Identification Cymrite can be identified by its characteristic pearly luster on cleavage surfaces, low hardness (can be scratched with a fingernail), and tendency to split into thin, flexible lamellae. Its occurrence in association with other barium minerals, such as baryte, can be an additional clue. ## Distinguishing from Similar Minerals Cymrite is sometimes confused with mica group minerals (e.g., muscovite) or talc due to similar luster and habit. However, it is distinguished by its higher density and characteristic occurrence environment, often associated with manganese deposits or metamorphism of barium-rich rocks. Chemical tests for the presence of barium allow for unambiguous differentiation from similar silicates. ## Crystal Forms Cymrite crystals are usually very small, with a tabular or platy habit, and a distinct hexagonal outline. They most often form radial, rosette-like, or scaly aggregates. Single, well-formed crystals are rarely found.
Geological environment
## Genesis Cymrite is a mineral formed under low-grade metamorphic conditions, especially in rocks rich in barium and silica. It often forms in quartz lenses within schists. Its formation is also associated with hydrothermal processes within manganese ore and metal sulfide deposits. ## Mineral Associations This mineral often co-occurs with other barium minerals, such as baryte and celsian. Depending on the location, it is also accompanied by quartz, calcite, zeolite group minerals, and in manganese deposits – rhodochrosite and other manganese oxides and silicates. ## Localities The most important cymrite localities in the world include the historical type locality in the Benallt mine in Wales (United Kingdom). Significant specimens also come from Schefferville in Quebec (Canada), the Keno Hill zinc-lead deposit (Yukon, Canada), and the Baikal region in Russia. It also occurs in several locations in the United States, including Alaska and California.
Rarity
Rare
For collectors
## Quality Criteria The most prized by collectors are specimens with well-formed, sharp crystals with a distinct hexagonal outline, forming aesthetic, rosette-like aggregates. The contrast with the rock matrix and the presence of associated minerals that highlight its genesis are also important. Due to the small size of the crystals, specimens with larger (above a few millimeters) and well-defined clusters are particularly sought after. ## Popular Localities Specimens from the type locality in Wales are of historical significance. However, the most visually attractive are often those from Canada (Quebec, Yukon), which are characterized by well-formed, white aggregates on a contrasting matrix.
Care and storage
## Cleaning Cymrite specimens should be cleaned very carefully due to their low hardness and perfect cleavage. It is recommended to use a soft brush to remove dust. For heavier soiling, compressed air can be used from a safe distance. Avoid contact with water, which can penetrate cleavage cracks. ## What to Avoid Avoid all hard tools, brushes, and ultrasonic cleaners, which can irreversibly damage or scratch delicate crystals. The mineral is sensitive to acids. It should not be heated or exposed to sudden temperature changes. ## Storage Cymrite should be stored in separate, padded boxes or containers to avoid contact with harder minerals that could scratch it. It is best displayed in closed display cases, protecting it from dust and mechanical damage.