Natrowalentaite
Chemical formula: [Fe<sup>3+</sup><sub>0.5</sub>Na<sub>0.5</sub>(H<sub>2</sub>O)<sub>6</sub>][NaAs<sup>3+</sup><sub>2</sub>(Fe<sup>3+</sup><sub>2.33</sub>W<sup>6+</sup><sub>0.67</sub>)(PO<sub>4</sub>)<sub>2</sub>O<sub>7</sub>]
Natrowalentite is an extremely rare, hydrated sodium, iron, and tungsten arsenate-phosphate, discovered in the Arsenatnaya mine in Russia.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- Light yellow
- Density
- 3.51
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of natrowalentite is impossible without advanced analytical methods. It requires chemical analysis (EDS) to confirm the presence of sodium, iron, tungsten, arsenic, and phosphorus, and X-ray diffraction (XRD) to confirm its unique crystal structure. Visually, at the occurrence site, it can be suspected based on its yellowish-brown color and its occurrence as small, bladed crystals in paragenesis with other rare arsenates. ## Distinguishing from Similar Minerals It can be confused with other minerals from the valentinite group, such as valentinite or arsenowaylandite, as well as with other secondary, yellow arsenates. Definitive distinction is only possible based on detailed chemical analysis, which will show the unique dominance of sodium for natrowalentite. ## Crystal Forms Natrowalentite forms very thin, tabular or bladed crystals, elongated in one direction. These crystals combine into radial, stellate, or haphazardly tangled aggregates.
Geological environment
## Genesis Natrowalentite is a fumarolic mineral. It forms as a result of resublimation of volcanic gases in oxidation zones at temperatures from 100 to 400°C. It crystallizes directly from hot vapors rich in arsenic, phosphorus, tungsten, and other elements on the surface of volcanic rocks. ## Mineral Associations This mineral co-occurs with other rare products of volcanic exhalations. At the type locality, it was found in association with hematite, tenorite, aphthitalite, johillerite, eriomenite, arseniopleite, badalovite, and svabite. ## Localities The only confirmed occurrence of natrowalentite in the world is its type locality – the Arsenatnaya fumarole, located on the second cinder cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption (1975-1976) on Tolbachik volcano, Kamchatka, Far Eastern Federal District, Russia.
Rarity
Extremely rare
For collectors
## Quality Criteria Due to the microscopic nature of the specimens, the main criterion for value is the richness and quality of the crystal aggregates on the rock matrix. The most desirable specimens are those with well-formed, abundant radial clusters of intense, yellowish-brown color. Association with other rare minerals from this locality is also important. ## Popular Localities The only source of natrowalentite specimens is its type locality – the Arsenatnaya fumarole on Tolbachik volcano in Russia. Material from this locality is extremely difficult to obtain and is a rarity in specialized collections of rare minerals and micromounts.
Care and storage
## Cleaning Due to extreme fragility, small size, and water solubility, natrowalentite specimens should not be wet cleaned. The safest method is to remove dust using compressed air from a safe distance or a very soft brush, if absolutely necessary. ## What to Avoid Contact with water, acids, and other chemicals that can dissolve or damage the mineral should be strictly avoided. Specimens are very sensitive to shocks and mechanical damage. They should not be heated or exposed to temperature changes. ## Storage Natrowalentite specimens, typically microscopic and on a rock matrix, should be stored in stable conditions, in closed, padded "micromount" boxes to protect them from dust, moisture, and physical damage. Vibrations should be avoided.