Qitianlingite
Chemical formula: Fe<sup>2+</sup><sub>2</sub>Nb<sup>5+</sup><sub>2</sub>W<sup>6+</sup>O<sub>10</sub>
Extremely rare iron, niobium, and tungsten oxide, forming tiny, black, metallic grains in granitic pegmatites.
Properties
- Mohs hardness
- 5.5
- Luster
- Metallic
- Streak
- Black
- Density
- 6.91
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Field identification of qitianlingite is impossible. Identification requires advanced laboratory techniques, such as chemical composition analysis (e.g., electron microprobe - EDS/WDS) and X-ray diffraction (XRD) to confirm the crystal structure. In a collection, it is a black, metallic mineral occurring as very fine grains in granitic rock. ## Distinguishing from Similar Minerals It can be confused with other black, metallic ore minerals found in pegmatites, such as columbite, tantalite, wolframite, or ilmenite. Differentiation from these is possible only through chemical analysis, which will show the simultaneous presence of niobium, tungsten, and iron in specific proportions. ## Crystal Forms Qitianlingite occurs as anhedral, irregular grains embedded in the host rock. It has not been observed in the form of well-developed crystals.
Geological environment
## Genesis Qitianlingite is a mineral of magmatic origin, crystallizing in the late stages of granite evolution and associated pegmatites. It forms in an environment rich in niobium, tungsten, and other rare elements, in greisenization zones (alteration of rocks under the influence of hot, water- and fluorine-rich fluids). ## Mineral Associations This mineral co-occurs with other minerals typical of granites and greisens, such as quartz, albite, muscovite, fluorite, cassiterite, wolframite, columbite-(Fe), and native bismuth. ## Localities The only confirmed occurrence of qitianlingite in the world is its type locality – the Qitianling granite massif in Rucheng County, Hunan Province, southern China.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a qitianlingite specimen is determined almost exclusively by its authenticity and analytical confirmation. Since the mineral occurs as microscopic grains, its aesthetic value is negligible. For collectors specializing in mineral systematics or rare species, the greatest value lies in a specimen with the highest concentration of qitianlingite grains, originating from the type locality, and preferably with accompanying analytical documentation. ## Popular Localities The only source of specimens is the type locality in the Qitianling massif in China. Any authentic specimen must originate from this single location.
Care and storage
## Cleaning Due to its extreme rarity and small specimen sizes, cleaning is usually neither necessary nor recommended. If the specimen is in its host rock, any chemical or mechanical interventions should be avoided. ## What to Avoid Contact with acids and other aggressive chemicals should be avoided. Specimens should be protected from mechanical damage, such as scratches or impacts, which could destroy the tiny mineral grains. ## Storage Qitianlingite specimens, typically as microscopic grains in host rock, should be stored under stable conditions, in specialized "micromount" boxes that protect them from dust and mechanical damage. Vibrations and shocks should be avoided.