Khurayyimite
Chemical formula: Ca₇Zn²⁺₄(Si₂O₇)₂(OH)₁₀·4H₂O
Khurayyimite is a rare zinc and calcium sorosilicate, forming colorless, platy crystals, discovered in Jordan.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- White
- Density
- 2.92
- Cleavage
- Perfect
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identifying khurayyimite in practice is impossible without advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). Preliminary identification based on appearance is difficult due to its microscopic, colorless crystals. Verification of co-occurring rare minerals from pyrometamorphic rocks is crucial. ## Distinguishing from similar minerals It can be confused with other colorless, microscopic silicates found in the same environment, such as gypsum, calcite, or other calcium silicates. Definitive differentiation requires specialized chemical and structural analysis. ## Crystal forms It forms aggregates of very small, thin, bladed or platy crystals, often arranged in rosettes or fan-like forms. The crystals are elongated in one direction and flattened.
Geological environment
## Genesis Khurayyimite forms as a result of pyrometamorphic processes in sedimentary rocks of the Hatrurim Formation (also known as the "Mottled Zone"). It forms in veins cutting through altered marls and limestones that have been subjected to high temperatures under low-pressure conditions, often due to the natural combustion of underground bitumen deposits. ## Mineral associations This mineral co-occurs with other rare pyrometamorphic products, such as afwillite, ettringite, calcite, jennite, tobermorite, as well as other calcium and zinc silicates. ## Localities The only confirmed occurrence of khurayyimite in the world is its type locality: Khurayyim Mountain in the Daba-Siwaqa complex, north of Amman in Jordan.
Rarity
Extremely rare
For collectors
## Quality criteria The quality of khurayyimite specimens is primarily assessed based on the richness and size of crystal aggregates on the rock matrix. Specimens with clearly visible, though still microscopic, rosettes or fans of crystals are most valued. The aesthetics of the matrix and the presence of contrasting associated minerals are also important. ## Popular localities The only source of specimens is the type locality in Jordan. Material from this location is extremely limited and rarely appears on the collector's market.
Care and storage
## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the microscopic size and delicacy of the crystals, any other method, including the use of water or brushes, risks their irreversible destruction. ## What to avoid Avoid contact with water, chemicals, ultrasound, and all forms of mechanical cleaning. The mineral is sensitive to acids. It should be protected from vibrations and impacts. ## Storage Specimens should be stored in stable, sealed "micromount" containers, protecting them from dust, moisture, and mechanical damage. Display should only be done under a microscope.