Kremersite
Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>Fe<sup>3+</sup>Cl<sub>5</sub>·H<sub>2</sub>O
Kremersite is a rare, water-soluble iron ammonium chloride, forming small, red crystals in volcanic environments.
Properties
- Mohs hardness
- 1-2
- Luster
- Vitreous
- Streak
- Orange-red
- Density
- 2.17
- Cleavage
- None
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
Diagnostic features
## Identification The key diagnostic feature of kremersite is its intense red color, occurrence as small, regular crystals, and genesis associated with volcanic fumaroles. The most important test, however, is its high water solubility, which immediately distinguishes it from most red minerals. ## Distinguishing from Similar Minerals Kremersite can be confused with other red secondary minerals, but its specific formation environment (volcanic exhalations) and water solubility are unique features. Other chlorides, such as molysite, usually have a different color (yellow, brown). ## Crystal Forms Kremersite crystallizes in the isometric system, most often forming small crystals with an octahedral or hexoctahedral habit. It occurs as efflorescences, crusts, and small crystalline aggregates on volcanic rocks.
Geological environment
## Genesis Kremersite is a mineral of volcanic origin, formed by sublimation from hot volcanic gases (exhalations). It crystallizes directly from the gas phase at temperatures from 100 to 600°C in the vicinity of fumaroles. ## Mineral Associations This mineral co-occurs with other chlorides and sulfates formed under similar conditions, such as sal ammoniac (ammonium chloride), halite (sodium chloride), sylvite (potassium chloride), and molysite (iron(III) chloride). ## Localities The most important and classic locality is the Vesuvius-Somma volcanic complex in Italy, where the mineral was first described. It has also been reported in exhalation products from Mount Etna in Sicily and from Tolbachik volcano in Kamchatka, Russia.
Rarity
Rare
For collectors
## Quality Criteria For collectors, the size and quality of crystal formation are most important. Specimens with well-formed, transparent, intensely red crystals, set on a contrasting matrix, are most valued. Due to its rarity, even microscopic but well-formed crystals have collector's value. ## Popular Localities By far the most valued and historically significant specimens come from Vesuvius in Italy. They represent a classic for this mineral. Specimens from Tolbachik volcano in Kamchatka have also yielded good quality crystals.
Care and storage
## Cleaning This mineral must absolutely not be wet cleaned. It is very soluble in water and will be destroyed upon contact with it or even with humid air. Specimens should only be cleaned mechanically, with a very soft-bristled brush or a stream of compressed air. ## What to Avoid Avoid all contact with water, water vapor, and high air humidity. Storage in a damp place (e.g., a basement) leads to rapid deliquescence, meaning the mineral dissolves in water absorbed from the air. It should also be protected from chemicals. ## Storage Kremersite specimens require storage in airtight conditions. The best solution is sealed plastic containers (so-called "perky boxes") or glass vials. It is advisable to place a desiccant (e.g., silica gel) inside to ensure a dry environment. Display should only take place in sealed display cases.