Hedyphane
Chemical formula: Ca₂Pb²⁺₃(As⁵⁺O₄)₃Cl
Hedyphane is a rare calcium lead arsenate from the apatite group, forming small, vitreous crystals with a whitish or yellowish hue.
Properties
- Mohs hardness
- 4-5
- Luster
- Vitreous
- Streak
- White
- Density
- 5.82
- Cleavage
- On <mi>{10_11}</mi>.
- Fracture
- Sub-Conchoidal
- Transparency
- Translucent to opaque
- Crystal system
- Hexagonal
Diagnostic features
## Identification Helpful features for identifying hedyphane include its high density (the specimen feels heavy for its size), vitreous luster, hexagonal crystal form, and occurrence in specific parageneses in metamorphic deposits. It reacts with hydrochloric acid. ## Distinguishing from Similar Minerals Hedyphane can be confused with other minerals from the apatite group, especially mimetite and pyromorphite. It is distinguished from them by its chemical composition (presence of calcium), which requires advanced analysis (e.g., EDS). Visually, it can be difficult to distinguish without knowing the locality and associated minerals. ## Crystal Forms Hedyphane crystals are typically short, prismatic, or barrel-shaped, with a hexagonal cross-section. They often occur as granular aggregates, radial aggregates, or as massive fillings.
Geological environment
## Genesis Hedyphane is a secondary mineral, formed as a result of metamorphic processes in iron and manganese ore deposits. It forms in rocks rich in calcium, lead, and arsenic, often in skarns or metamorphosed carbonate rocks. ## Mineral Associations This mineral often co-occurs with other minerals characteristic of metamorphosed ore deposits. Its typical associations include: baryte, hausmannite, braunite, magnetite, berzeliite, caryopilite, and richterite. ## Localities The most important and classic locality for hedyphane is the Långban mine in Värmland, Sweden, from which the type material originates. Other known localities include the Franklin mine in New Jersey (USA), where well-formed crystals were found, as well as Tsumeb in Namibia and Broken Hill in Australia.
Rarity
Rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp crystals with a distinct luster. Crystal size is also important – larger specimens are much rarer. A contrasting substrate (rock matrix) and association with other rare minerals enhance its attractiveness. ## Popular Localities Specimens from historical localities, such as Långban in Sweden and Franklin in the USA, are considered classics and hold particular value for collectors. However, material from these locations is difficult to obtain on the market.
Care and storage
## Cleaning Hedyphane specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Due to the presence of lead and arsenic, hands should be washed after contact with the mineral. ## What to Avoid Contact with acids and other aggressive chemicals that can damage the mineral's surface should be avoided. Hedyphane is brittle, so it must be protected from impacts and falls. It should not be heated or subjected to ultrasound. ## Storage Hedyphane specimens are best stored in separate, padded collector boxes to prevent scratches from harder minerals. It should be protected from dust and moisture. Exposure to direct sunlight is not recommended, although there is no evidence of it fading.