Lisiguangite

Chemical formula: Cu₁+Pt₂+Bi₃+S₂-₃

Lisiguangite is an extremely rare copper, platinum, and bismuth sulfide, occurring as microscopic grains in ultramafic rocks.

## Characteristics Lisiguangite is a sulfide mineral that, due to its rarity and microscopic size, is primarily of scientific interest. It occurs as anhedral (irregularly shaped) grains, typically not exceeding 100 micrometers in size. It is opaque, with a metallic luster and a steel-gray color with a slight, creamy tint. When observed under a microscope in reflected light, its color is described as grayish-white. ## Physical Properties The mineral's hardness on the Mohs scale is estimated to be around 4-4.5. It is a brittle mineral. The density calculated based on its chemical composition and unit cell parameters is 8.55 g/cm³. It possesses a strong, metallic luster and is completely opaque. ## Colors and Varieties The mineral is color-homogeneous – its color is steel-gray, grayish-white, or creamy-gray. No color varieties or commercial forms are distinguished. ## History and Name Lisiguangite was first described in 1997 by Yu Zuxiang. Its name commemorates Professor Li Siguang (1889–1971), a distinguished Chinese geologist and founder of geomechanics in China. The type locality from which it originates is the Baimazhai copper-nickel deposit in Yunnan Province, China. ## Applications Due to its extreme rarity and microscopic size, lisiguangite has no commercial or industrial applications. It is solely an object of scientific research, particularly in the field of mineralogy and platinum-group element deposit geology.

Properties

Mohs hardness: 4-4.5
Luster: Metallic
Streak: Black
Density: 8.55
Cleavage: None
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of lisiguangite is impossible without advanced analytical techniques. Due to its microscopic size and occurrence as inclusions within other minerals, identification relies on chemical composition analysis using an electron microprobe (EDS/WDS). In reflected light under a polarizing microscope, it exhibits weak anisotropy. ## Distinguishing from Similar Minerals Visually, it is practically indistinguishable from other microscopic sulfides and platinum-group minerals with which it coexists, such as bornite, chalcopyrite, cubanite, cooperite, or vysotskite. Definitive differentiation is only possible through chemical analysis, which reveals a unique combination of copper, platinum, and bismuth. ## Crystal Forms This mineral does not form well-developed crystals. It occurs exclusively as irregular, anhedral grains and aggregates, often as inclusions within other sulfides, mainly bornite.

Geological environment

## Genesis Lisiguangite is a magmatic mineral. It forms in the final stages of magma crystallization within mineralized mafic and ultramafic intrusions (e.g., peridotites). It crystallizes from residual, sulfide- and platinum-group element-rich sulfide melts. ## Mineral Associations This mineral occurs in association with other copper, iron, and nickel sulfides, and platinum-group minerals. It most commonly coexists with bornite, chalcopyrite, cubanite, pentlandite, cooperite, braggite, vysotskite, and native platinum. ## Localities It is an extremely rare mineral, known from only a few localities worldwide. The type locality is the Baimazhai Cu-Ni deposit in Yunnan (China). Its presence has also been confirmed in deposits in the Noril'sk region in Siberia (Russia) and in the Bushveld Complex in South Africa.

Rarity

Extremely rare

For collectors

## Quality Criteria Lisiguangite is not a collector's mineral in the traditional sense. Specimens have scientific value only. In this context, a "high-quality" specimen can be considered a polished petrographic thin section with a clearly identified and analyzed grain of lisiguangite, along with complete analytical documentation. ## Popular Localities Specimens are not available on the collector's market. The only known samples are in the collections of scientific institutions and originate from research localities such as Baimazhai in China or Noril'sk in Russia.

Care and storage

## Cleaning Lisiguangite specimens are typically scientific preparations in the form of polished sections or micromounts. They do not require cleaning. If dusty, a photographic air blower can be used to remove dust. Any contact with water and chemical agents should be avoided. ## What to Avoid As a sulfide, the mineral may be sensitive to oxygen and moisture, which can lead to its slow oxidation. Contact with acids and other chemicals should be avoided, as well as cleaning in ultrasonic cleaners, which could damage the delicate specimen. ## Storage Specimens should be stored under stable conditions in a dry environment. The best solution is a dedicated micromount box that protects against dust, moisture, and mechanical damage.

Sources

IMA Mineral List (CNMNC)