Nitromagnesite
Chemical formula: Mg(N<sup>5+</sup>O<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O
Nitromagnesite is a water-soluble, hydrated magnesium nitrate, forming efflorescences and crusts in dry caves and mines.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- White
- Density
- 1.55
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification The key diagnostic feature of nitromagnesite is its immediate and complete solubility in water. Its occurrence as delicate, white, acicular or fibrous efflorescences in dry caves or old mine workings is very characteristic. It is very soft and feels like glass wool to the touch. ## Distinguishing from Similar Minerals Nitromagnesite can be confused with other soluble nitrates or sulfates that form efflorescences, such as nitrocalcite, epsomite, or gypsum. It differs from nitrocalcite in chemical composition (magnesium instead of calcium), which requires chemical analysis. From epsomite and gypsum (sulfates), it can be distinguished by chemical tests for the presence of nitrate ions. In practice, the environment of occurrence and extreme hygroscopicity are key. ## Crystal Forms Crystals are typically acicular or hair-like, elongated along one axis. Most often, it forms fibrous aggregates, radial aggregates, as well as delicate crusts and efflorescences on rock surfaces.
Geological environment
## Genesis Nitromagnesite is a secondary mineral, formed by the evaporation of solutions rich in magnesium and nitrate ions. It forms in dry places sheltered from rain, such as caves, rock fissures, and old mine workings. The source of nitrates is often the bacterial decomposition of organic matter, especially animal droppings (e.g., bat or bird guano), which react with magnesium minerals in rocks (e.g., dolomite, magnesite). ## Mineral Associations It often co-occurs with other similar, soluble evaporite minerals, such as nitrocalcite, epsomite, gypsum, as well as with calcite and dolomite, which constitute the host rock. ## Localities Nitromagnesite is found in many caves and dry regions worldwide. Known localities include caves in Kentucky (e.g., Mammoth Cave), Tennessee, and Alabama in the USA, as well as in caves and mines in Europe, e.g., in Italy (Vesuvius area) and Germany.
Rarity
Not very common
For collectors
## Quality Criteria The collector's appeal of nitromagnesite primarily depends on the abundance and form of its crystals. The most prized specimens are those with well-formed, long needles or rich, "fluffy" fibrous aggregates covering a fragment of the host rock. Purity (snow-white color) and absence of mechanical damage are also important, which is difficult to achieve due to the mineral's delicacy. ## Popular Localities Classic and valued specimens come from cave systems in Kentucky and Tennessee in the USA, where this mineral was exploited on a small scale in the 19th century for gunpowder production.
Care and storage
## Cleaning Nitromagnesite is extremely water-soluble, so **it must never be cleaned with water or any liquids**. The only safe method is to very carefully remove dust using a soft, dry brush or a gentle stream of compressed air from a distance. ## What to Avoid Contact with water, water vapor, and high air humidity, which will cause the specimen to dissolve and be destroyed, must be strictly avoided. The mineral is very soft and brittle, susceptible to the slightest mechanical damage. It should be protected from all chemicals. ## Storage Nitromagnesite specimens must be stored under controlled, very low humidity conditions. The best solution is a sealed container (e.g., a "perky box") with a desiccant (e.g., silica gel). Avoid exposure to open air.