Strontiomelane
Chemical formula: Sr(Mn<sup>4+</sup><sub>6</sub>Mn<sup>3+</sup><sub>2</sub>)O<sub>16</sub>
Strontiomelane is a rare strontium and manganese oxide, forming black, fibrous or radial aggregates with a metallic luster.
Properties
- Mohs hardness
- 5-6
- Luster
- Metallic
- Streak
- Black
- Density
- 4.66
- Cleavage
- Good on {110}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Strontiomelane is identified by its black color, metallic luster, and characteristic forms of occurrence – radial or fibrous aggregates. Hardness (5-6) and a black streak are also important indicators. However, final confirmation requires advanced chemical analysis (EDS) to confirm the presence of strontium as the dominant element. ## Distinguishing from Similar Minerals This mineral is difficult to distinguish from other black manganese oxides of the hollandite and cryptomelane groups, such as hollandite, cryptomelane, or manjiroite. Visually, they can be identical. Reliable differentiation is possible almost exclusively by chemical analysis (e.g., EDS, WDS) to determine which element (Ba, K, Na, Sr) dominates in a given specimen. ## Crystal Forms Most often, it forms fibrous, radial, spherulitic aggregates, as well as compact and massive clusters. Single, small crystals with a prismatic habit, elongated along the [001] axis, are rarely observed.
Geological environment
## Genesis Strontiomelane is a mineral of hydrothermal origin. It forms at low to medium temperatures in ore veins, where it crystallizes from solutions rich in manganese and strontium. It is a product of the alteration of earlier manganese minerals. ## Mineral Associations It most often co-occurs with other manganese oxides, such as hollandite, cryptomelane, pyrolusite, and romanechite. It is also accompanied by calcite, quartz, barite, and various sulfides. ## Localities The most important and classic localities for this mineral are: - Salsigne, Aude department, France (type locality). - Fianel Mine, Ferrera Valley, Graubünden, Switzerland. - Långban, Filipstad, Värmland, Sweden. - Valgraveglia Mine, Liguria, Italy. - Broken Hill, New South Wales, Australia.
Rarity
Very rare
For collectors
## Quality Criteria The most valued by collectors are specimens with well-formed, radial aggregates with a distinct, metallic luster. Contrast with a light matrix rock (e.g., with quartz or calcite) enhances attractiveness. The size of the aggregates and confirmation of the mineral's identity are also important, which is crucial due to its similarity to other manganese oxides. ## Popular Localities Specimens from the type locality (Salsigne, France) and the Swiss Fianel mine are most sought after by collectors due to their historical and scientific significance.
Care and storage
## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush or a small brush to remove dust. Compressed air can be used. The use of water is not recommended, especially for specimens on a delicate matrix. ## What to Avoid Contact with acids and other chemicals that can react with manganese oxides must be strictly avoided. The mineral is brittle and sensitive to impact. It should not be heated or cleaned in ultrasonic cleaners. ## Storage Store in stable conditions, away from moisture and dust, preferably in a closed display box or cabinet. Avoid placing heavier minerals on delicate, fibrous strontiomelane aggregates.