Apexite
Chemical formula: NaMg(PO<sub>4</sub>)·9H<sub>2</sub>O
Apexite is a rare, hydrated sodium and magnesium phosphate, forming colorless, bladed crystals, discovered in the Apex mine in Nevada.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- White
- Density
- 1.99
- Cleavage
- Perfect on {010}
- Fracture
- Splintery
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Apexite can be identified by its characteristic, colorless, bladed crystals forming rosette-like aggregates. Its very low hardness (approximately 2), flexibility of fibers, and vitreous luster are key features. Its occurrence in association with other rare phosphates in the Apex mine is also an important clue. ## Distinguishing from similar minerals It can be confused with other colorless, secondary phosphate minerals such as struvite or newberyite. Differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS), due to visual similarity and occurrence in similar environments. However, its flexibility is a distinguishing feature. ## Crystal forms Crystals are thin, tabular or bladed, elongated along the [100] axis and flattened parallel to {010}. They usually occur as radial or rosette-like aggregates, as well as clusters of flexible fibers.
Geological environment
## Genesis Apexite is a secondary mineral that formed as a result of low-temperature hydrothermal processes. It crystallizes from relatively undiluted solutions rich in phosphorus, sodium, and magnesium. At its type locality (Apex mine), it formed in the oxidation zone of a copper deposit, within a sedimentary breccia in the Kaibab Formation. ## Mineral associations In the Apex mine, apexite co-occurs with other rare phosphate and sulfate minerals, such as: ankinovichite, koninckite, newberyite, schertelite, struvite, satterlyite, as well as gypsum and quartz. ## Localities The only confirmed and described locality of apexite in the world is the Apex mine in the St. George district, Washington County, Nevada, USA. This is its type locality.
Rarity
Very rare
For collectors
## Quality criteria The quality of an apexite specimen is assessed based on the size and development of the crystals and the richness of aggregates on the rock matrix. The most desirable specimens are those with distinct, well-formed, transparent crystals forming aesthetic, rosette-like clusters. Association with other rare minerals from this locality is also important. Due to the microscopic nature of most specimens, their photogenicity under magnification is crucial. ## Popular localities The only source of apexite specimens is its type locality – the Apex mine in Nevada, USA. This mine is known among collectors for the occurrence of many rare secondary minerals, which makes specimens from there particularly interesting.
Care and storage
## Cleaning Due to its extreme delicacy and softness, mechanical cleaning is highly inadvisable. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust. Contact with water, which can damage or dissolve the mineral, should be avoided. ## What to avoid Contact with water and other chemicals must be strictly avoided. The mineral is very soft, susceptible to scratches and mechanical damage. It should be protected from high temperatures and direct sunlight, which can lead to dehydration and destruction of the crystals. ## Storage Apexite specimens should be stored exclusively in closed, stable "micromount" containers to protect them from dust, moisture, and physical damage. Crystals should not be touched with bare hands. Store in a dry place at a constant temperature.