Chayesite
Chemical formula: KMg₄Fe³⁺[Si₁₂O₃₀]
Chayesite is a very rare mineral from the osumilite group, distinguished by its intensely blue color and occurrence in volcanic lamproites.
Properties
- Mohs hardness
- 5-6
- Luster
- Vitreous
- Density
- 0
- Transparency
- Transparent
- Crystal system
- Hexagonal
Diagnostic features
## Identification The key diagnostic features of chayesite are its intensely blue color, hexagonal crystal habit, and specific occurrence environment – lamproites. A hardness of 5-6 on the Mohs scale and vitreous luster are also helpful in identification. However, definitive confirmation requires advanced analytical methods, such as chemical composition analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Blue chayesite is sometimes confused with other blue minerals found in similar parageneses, such as sapphirine. Distinguishing it with the naked eye is practically impossible and requires laboratory analysis. It differs from them in chemical composition and crystal structure. ## Crystal Forms Chayesite forms hexagonal, tabular or platy crystals, often grouped into small aggregates. Crystals are usually small, rarely exceeding a few millimeters, and most often occur as inclusions in the rock.
Geological environment
## Genesis Chayesite is a mineral of magmatic origin. It forms in the final stages of crystallization in potassium-rich, silica-undersaturated volcanic rocks, known as lamproites. It crystallizes under conditions of high temperature and relatively low pressure, typical of lava flows. ## Mineral Associations This mineral co-occurs with other silicates characteristic of lamproites. The most common associated minerals include sanidine, diopside, phlogopite, richterite, wadeite, and titanium oxides like priderite. ## Localities Chayesite is an extremely rare mineral, known from only a few localities worldwide. The most important and classic occurrences are: - Type locality: Moon Canyon, Woodland, Summit County, Utah, USA. - Other confirmed occurrences: Smoky Butte, Garfield County, Montana, USA; West Kimberley, Australia; and the Murcia region in Spain.
Rarity
Very rare
For collectors
## Quality Criteria The most highly valued chayesite specimens are those that contain well-formed, sharply defined crystals of intense, sapphire blue color. Contrast with a lighter host rock (matrix) significantly enhances visual appeal. Crystal size is a key factor – specimens with crystals exceeding 1-2 mm are already considered exceptional. Crystal clarity and transparency also affect value. ## Popular Localities The most known and prized specimens by collectors come from two localities in the USA: Smoky Butte in Montana and the discovery site in Moon Canyon in Utah. Specimens from these localities are considered the global standard for this mineral.
Care and storage
## Cleaning Chayesite specimens, usually embedded in a rock matrix, should be cleaned very carefully. It is recommended to use a soft brush to remove dust. For heavier dirt, compressed air (from a safe distance) or a damp cloth with distilled water can be used, avoiding soaking the entire rock. ## What to Avoid Avoid contact with acids and strong chemical agents, which can damage both the mineral itself and the host rock. Although its light stability is not fully researched, it is recommended to avoid prolonged exposure to direct sunlight to prevent potential fading. ## Storage Specimens should be stored in stable conditions, away from dust and moisture. It is best to place them in sealable display boxes or cabinets, protecting them from mechanical damage and sudden temperature changes.