Blödite
Chemical formula: Na<sub>2</sub>Mg(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O
Blödite is a hydrated sodium magnesium sulfate, typically forming granular or massive aggregates, less commonly well-formed crystals.
Properties
- Mohs hardness
- 2.5-3
- Luster
- Vitreous
- Streak
- White
- Density
- 2.2-2.3
- Cleavage
- Perfect on {100}, less perfect on {011}
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Key diagnostic features of blödite are its low hardness, solubility in water, and bitter-salty taste. Its occurrence in salt evaporites is also a strong indicator. In dry air, it may become covered with a white, powdery coating of dehydration products. ## Distinguishing from Similar Minerals It can be confused with other evaporites, such as halite, gypsum, or epsomite. It differs from halite in taste (bitter-salty, not salty) and crystal form. It is much more soluble in water than gypsum. Epsomite is usually more fibrous and has a different chemical composition. ## Crystal Forms Crystals, though rare, are monoclinic and take the form of short, thick prisms or thick tabular crystals. They often occur as massive, granular, or botryoidal aggregates within salt rocks.
Geological environment
## Genesis Blödite is a typical evaporite mineral. It forms as a result of the evaporation of saline lake waters or closed marine basins, rich in sodium and magnesium sulfates. It crystallizes in environments with high salt concentrations, under dry and hot climatic conditions. ## Mineral Associations It most commonly co-occurs with other salt minerals, such as halite, sylvite, carnallite, epsomite, gypsum, mirabilite, and thenardite. ## Localities Significant deposits and well-formed crystals come from salt mines in Bad Ischl and Hallstatt in Austria. It also occurs in deposits in Germany (Stassfurt), Italy (Sicily), USA (Great Salt Lake in Utah, deposits in California and New Mexico), Chile (Atacama Desert), and China (Xinjiang province).
Rarity
Not very common
For collectors
## Quality Criteria Large, well-formed, and transparent blödite crystals are most valued by collectors, though they are very rare. Specimens with clear associations with other colorful evaporite minerals are also attractive. Due to the mineral's instability, the perfect state of preservation of the specimen, without signs of weathering or decomposition, is crucial. ## Popular Localities The classic localities in Austria (Bad Ischl, Hallstatt), from which historical specimens originate, are considered the best for this mineral. Large and well-formed crystals are also found in some dried lakes in the USA (Soda Lake in California) and in China.
Care and storage
## Cleaning Blödite is very sensitive to water and moisture. It should not be cleaned wet. To remove dust, a very soft, dry brush or compressed air from a safe distance can be used. ## What to Avoid Contact with water, water vapor, and humid air must be absolutely avoided, as the mineral readily dissolves and dehydrates, turning into dust. It should be protected from high temperatures and direct sunlight, which can accelerate decomposition processes. ## Storage Blödite specimens require special storage conditions. They are best kept in tightly sealed containers or boxes with a moisture absorber (e.g., silica gel). Display should be in dry, air-conditioned display cases.