Potassic-chloro-pargasite
Chemical formula: KCa₂(Mg₄Al)(Si₆Al₂)O₂₂Cl₂
Potassic-chloro-pargasite is a rare mineral from the amphibole group, distinguished by the presence of potassium and chlorine in its complex chemical structure.
Properties
- Mohs hardness
- 5.5-0
- Luster
- Vitreous
- Streak
- White
- Density
- 3.29
- Cleavage
- Perfect {110}.
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identifying potassic-chloro-pargasite in field conditions or in a collection is practically impossible without advanced analysis. Its appearance is very similar to other dark amphiboles, such as hornblende or other minerals from the pargasite group. Dark green to black color, vitreous luster, and prismatic habit are general characteristics of amphiboles. Definitive identification requires chemical analysis (e.g., EDS) to confirm the dominance of potassium and chlorine. ## Distinguishing from Similar Minerals It can be confused with numerous minerals from the amphibole group, especially hornblende, ferro-pargasite, magnesio-hastingsite, or other pargasites. The differences between them are subtle and based on the proportions of elements (K, Na, Cl, OH, Fe, Mg), which is impossible to assess visually. It can be distinguished from pyroxenes (e.g., augite) by the cleavage angle (approx. 120° for amphiboles, approx. 90° for pyroxenes), although this feature is difficult to observe in fine-grained aggregates. ## Crystal Forms It forms elongated, prismatic crystals, often with a hexagonal cross-section. It also occurs as fibrous, radial, or granular aggregates, intergrown in the host rock.
Geological environment
## Genesis Potassic-chloro-pargasite is a metamorphic mineral. It forms under conditions of high-grade metamorphism, in the amphibolite and granulite facies. Its formation is associated with the presence of potassium and chlorine in metamorphic fluids, which react with the primary minerals of the rock. ## Mineral Associations It co-occurs with other minerals typical of high-grade metamorphic rocks, such as diopside, scapolite, phlogopite, titanite, calcite, and other amphiboles and pyroxenes. ## Localities This is a very rare mineral. Its occurrence has been confirmed in only a few places worldwide. One of the key localities is the Pargas metamorphic complex in Finland, from which the entire pargasite group takes its name. Other confirmed occurrences include the Bancroft area in Ontario (Canada) and some localities in the USA.
Rarity
Very rare
For collectors
## Quality Criteria As an extremely rare mineral, every analytically confirmed specimen has high scientific and collector value. The most desirable specimens are those with well-formed, visible crystals, even if small. Contrast with a light host rock (e.g., calcite) significantly enhances visual appeal. However, the key factor for value is certainty of identification, supported by chemical analysis. ## Popular Localities Specimens from the type locality (Pargas, Finland) or from classic Canadian localities (Ontario) are most highly prized by specialized collectors of rare minerals.
Care and storage
## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush or compressed air to remove dust. Due to its rarity and potential reactivity, avoiding contact with water and chemicals is the safest approach. ## What to Avoid Avoid contact with all acids and chemicals that may react with the mineral's complex structure. It should not be heated or subjected to ultrasound. Prolonged exposure to moisture can be harmful. ## Storage Store in stable conditions, away from sources of moisture and chemical contaminants. It is best kept in a closed display box or cabinet to protect delicate crystals from mechanical damage and dust.