Verplanckite
Chemical formula: Ba₄Mn²⁺₂Si₄O₁₂(OH,H₂O)₃Cl₃
Verplanckite is a very rare silicate mineral, forming unique, prismatic crystals with a hexagonal outline and a characteristic brown color.
Properties
- Mohs hardness
- 2.5-3
- Color
- Brown-yellow, may have an orange tint
- Luster
- Vitreous
- Streak
- Pale orange
- Density
- 3.52
- Cleavage
- Good on<mi> {11_20}</mi>; on {0001}, poor or a fracture.
- Fracture
- Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Hexagonal
Diagnostic features
## Identification The key diagnostic feature of verplanckite is its characteristic habit of hexagonal, prismatic crystals with a brown color. Combined with its extremely rare occurrence and specific geological environment (metamorphic rocks rich in barium), these features are usually sufficient for identification. ## Distinguishing from Similar Minerals Due to its unique form and composition, verplanckite is difficult to confuse with other minerals, especially if the specimen's origin is known. Theoretically, some brown tourmalines or cassiterite crystals might exhibit a similar habit, but they differ significantly in hardness, density, and occurrence environment. ## Crystal Forms Verplanckite forms well-developed, elongated prismatic crystals with a hexagonal cross-section. The crystals are terminated by flat pinacoids. They occur as single crystals or in small groups.
Geological environment
## Genesis Verplanckite is a mineral of metamorphic origin. It forms in sanbornite-quartz lenses within rocks that have undergone contact metamorphism. Its crystallization occurs under specific conditions, with the presence of barium, manganese, and chlorine. ## Mineral Associations This mineral is associated with other rare barium minerals, such as sanbornite, gillespite, muirite, fresnoite, as well as quartz, celsian, and diopside. ## Localities The only known and confirmed occurrence of verplanckite in the world is its type locality: the Rush Creek (or Big Creek) deposit in Fresno County, California, USA. It is an endemic mineral to this single locality.
Rarity
Very rare
For collectors
## Quality Criteria Most prized by collectors are well-formed, sharply terminated, single crystals with a distinct hexagonal outline and good luster. Crystal size is of great importance – specimens exceeding 1 cm are considered exceptional. The attractiveness is also enhanced by the contrasting placement of a brown crystal on a light matrix, e.g., on white quartz or sanbornite. ## Popular Localities As verplanckite occurs in only one place in the world – Big Creek, California – all collector specimens originate from this locality.
Care and storage
## Cleaning Due to its low hardness and potential reactivity, the utmost caution is recommended. The safest way to remove dust is with a soft brush or compressed air from a safe distance. Avoid washing in water, especially in acidic or alkaline solutions. ## What to Avoid Avoid contact with chemicals, including acids and detergents. The mineral is soft and susceptible to scratches, so it must be protected from contact with harder minerals. It should not be heated or subjected to ultrasound. ## Storage Verplanckite specimens are best stored in separate, padded display boxes to prevent abrasion and mechanical damage. They should be protected from dust and moisture.