Dessauite-(Y)
Chemical formula: Sr<sup>2+</sup>(Y,U<sup>4+</sup>,Mn<sup>2+</sup>)Fe<sup>3+</sup><sub>2</sub>(Ti<sup>4+</sup>,Fe<sup>3+</sup>,Cr<sup>3+</sup>,V<sup>5+</sup>)<sub>18</sub>(O,OH)<sub>38</sub>
Dessauite-(Y) is a very rare, black oxide mineral from the crichtonite group, distinguished by its complex chemical composition with yttrium, strontium, and titanium.
Properties
- Mohs hardness
- 7.5 - 8
- Luster
- Metallic, Submetallic
- Streak
- Black
- Density
- 4.73
- Cleavage
- None
- Fracture
- Uneven, Conchoidal
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Dessauite-(Y) is difficult to identify visually without advanced research methods. Its key features include black color, strong metallic luster, high hardness (7.5-8), and characteristic hexagonal crystal shape. It occurs as very small, tabular crystals, often embedded in calcite. ## Distinguishing from Similar Minerals It can be confused with hematite, ilmenite, magnetite, or other minerals from the crichtonite group. It differs from hematite by the absence of a reddish-brown streak (dessauite's streak is black). It differs from magnetite by the lack of magnetic properties. Definitive distinction from ilmenite and other members of the crichtonite group requires chemical analysis (EDS/WDS) to confirm the dominance of yttrium, strontium, and titanium. ## Crystal Forms Crystals are typically small, tabular, flattened parallel to the basal plane, or short-prismatic. They have a clearly visible hexagonal outline.
Geological environment
## Genesis Dessauite-(Y) forms as a result of metamorphic processes. In its type locality (Buca della Vena, Italy), it occurs in hydrothermal calcite veins cutting dolomitic marbles containing hematite and sulfides. Its formation is linked to the mobilization and concentration of rare-earth elements, titanium, and strontium under specific geochemical conditions. ## Mineral Associations This mineral coexists with minerals such as calcite, hematite, pyrite, derricksite, and other rare minerals from the crichtonite group. ## Localities The most important and type locality for dessauite-(Y) is the Buca della Vena mine in the municipality of Stazzema, in the Apuan Alps (Tuscany, Italy). This is the only confirmed and well-documented locality for this mineral worldwide.
Rarity
Extremely rare
For collectors
## Quality Criteria The collector appeal of dessauite-(Y) primarily depends on the quality and size of the crystals. Most valued are specimens with sharply defined, well-formed, lustrous crystals that clearly stand out from the surrounding matrix (most often white calcite). Crystal size is a key factor – any specimen with crystals exceeding 2-3 mm is considered exceptional. ## Popular Localities The only source of collector specimens is the Buca della Vena mine in Italy. Material from this locality is highly sought after by collectors specializing in "microminerals" and rare and systematic minerals.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to the possible presence of radioactive elements (uranium), avoid inhaling dust and wash hands after handling the mineral. ## What to Avoid Avoid contact with strong acids and chemicals. Despite its high hardness, the mineral is brittle and should be protected from impacts and falls. It does not require special protection from light or temperature, but storage in stable conditions is recommended. ## Storage It is recommended to store specimens in separate, padded collector boxes (e.g., "membrane box" or foam-lined box) to prevent mechanical damage. Specimens should be properly labeled, taking into account their potential, though usually low, radioactivity.