Tianhongqiite
Chemical formula: Cr<sup>3+</sup>Ti<sup>4+</sup>O<sub>3</sub>(OH)
Tianhongqiite is an extremely rare chromium and titanium oxyhydroxide, found only as microscopic grains in Tibetan chromitites.
Description
## Characteristics Tianhongqiite is a black mineral with a submetallic luster. It occurs as anhedral (irregular), microscopic grains, usually not exceeding a few tens of micrometers in size. Due to its size, its visual features are impossible to observe with the naked eye and require significant magnification. It is opaque. ## Physical Properties The hardness of the mineral has not yet been determined. It has a calculated density of approximately 4.35 g/cm³. It is characterized by a submetallic luster and a black streak. ## Colors and Varieties The mineral is uniformly black. No varieties have been distinguished. ## History and Name Tianhongqiite was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2019. Its name honors Chinese geologist Tian Hongqi, a specialist in the study of ophiolites and chromitites. It was discovered in the Luobusha ophiolite massif in Tibet. ## Applications Due to its extreme rarity and microscopic size, tianhongqiite has no commercial or industrial applications. It is solely an object of scientific research and is of interest to specialized micromineral collectors.
Diagnostic features
## Identification Identification of tianhongqiite is impossible without advanced analytical techniques, such as electron probe microanalysis (EPMA/WDS). A key diagnostic feature is its unique chemical composition – it is a chromium and titanium oxyhydroxide. ## Distinguishing from Similar Minerals In polished samples, it is practically indistinguishable from co-occurring minerals such as chromite, magnetite, ilmenite, or other rare oxides. It differs from them in chemical composition, which requires specialized analysis. ## Crystal Forms It occurs exclusively as anhedral (irregular) grains. No well-formed crystals have been observed.
Geological environment
## Genesis Tianhongqiite forms under specific geological conditions, in chromitite rocks that are part of ophiolite massifs. Its genesis is associated with metamorphic processes occurring under ultra-high pressure in subduction zones, within the Earth's mantle. ## Mineral Associations It co-occurs with chromite, as well as with other rare minerals such as qingsongite, wuyanzhiite, coesite, diamond, and various titanium and chromium oxides. ## Localities The only confirmed locality of tianhongqiite in the world is the Luobusha ophiolite in Qusum County, Tibet (China).
Rarity
Extremely rare
Collector aspects
## Quality Criteria In the case of such a rare micromineral, the only criterion is the confirmation of its presence in the sample itself. A collectible specimen is typically a fragment of the host rock (chromitite) with a precisely located and studied tianhongqiite grain, often in the form of a polished sample (thin section). ## Popular Localities The only source of specimens is the type locality in Tibet.
Care and storage
## Cleaning Specimens of this mineral are typically embedded in resin and polished samples for microscopic examination or individual grains in special boxes. They do not require and should not be cleaned in a traditional manner. ## What to Avoid Avoid contact with chemicals, ultrasound, and any attempts at mechanical cleaning, which could damage or lose the microscopic specimen. ## Storage Store exclusively in dedicated micromineral boxes (micromounts), protecting them from dust and shocks.