Gravegliaite
Chemical formula: Mn²⁺S⁴⁺O₃·3H₂O
Gravegliaite is a very rare, colorless manganese sulfite, forming tiny, acicular crystals in manganese deposits.
Properties
- Luster
- Vitreous
- Streak
- White
- Density
- 0
- Cleavage
- Parallel to [010].
- Fracture
- None observed
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Identification of gravegliaite is primarily based on its characteristic appearance – it forms colorless, acicular or bladed crystals gathered in radial aggregates. Its locality and co-occurrence with other manganese minerals, such as rhodochrosite or hausmannite, are crucial. Due to the small size of the crystals, identification usually requires magnification. ## Distinguishing from Similar Minerals It can be confused with other secondary sulfate or silicate minerals with an acicular habit. Differentiation from similar minerals, such as gypsum or some zeolites, is possible based on chemical analysis (EDS/XRD) and knowledge of the paragenesis (associated minerals) typical for manganese deposits. ## Crystal Forms Gravegliaite crystallizes in the form of very fine, elongated crystals with an acicular habit or thin blades. These crystals often form radial or chaotically arranged aggregates, as well as small crusts on the surface of the host rock.
Geological environment
## Genesis Gravegliaite is a secondary mineral, formed as a result of hydrothermal processes or weathering within manganese deposits. Its formation is associated with low-temperature solutions containing sulfites, which react with manganese minerals under specific reducing conditions. ## Mineral Associations This mineral occurs in association with other manganese minerals. In its type locality (Gambatesa mine), it co-occurs with rhodochrosite, hausmannite, braunite, ganophyllite, saneroite, pyrochroite, and calcite. ## Localities The only confirmed and most important occurrence of gravegliaite in the world is the Gambatesa mine, located in the municipality of Ne, in Liguria, Italy. This is its type locality and practically the only source of specimens of this mineral.
Rarity
Very rare
For collectors
## Quality Criteria The quality of gravegliaite specimens is primarily assessed based on the abundance and development of crystals. The most valued samples are those with rich, well-formed, radial aggregates of colorless needles, clearly visible against a contrasting background of the host rock (e.g., on pink rhodochrosite). The size of the aggregates and the absence of mechanical damage are also important. ## Popular Localities The only source of collectible gravegliaite specimens is its type locality – the Gambatesa mine in Italy. Specimens from this location are highly sought after by collectors specializing in rare minerals and systematic minerals.
Care and storage
## Cleaning Gravegliaite specimens are extremely delicate and sensitive to chemical changes. Mechanical cleaning is highly risky. If absolutely necessary, compressed air can be used from a distance to remove loose dust. Any contact with water and chemicals should be avoided. ## What to Avoid The mineral is unstable and easily oxidizes, especially in a humid environment. Contact with water, acids, cleaning agents, and high air humidity must be strictly avoided. It should be protected from direct sunlight and temperature changes. ## Storage Specimens should be stored in sealed, transparent containers (so-called "perky boxes") away from sources of moisture and light. It is best to place a desiccant (e.g., silica gel) inside the container. Due to its fragility, the container should protect the specimen from shocks and vibrations.