Sugakiite

Chemical formula: Cu(Fe,Ni)₈S₈

Sugakiite is a rare copper, iron, and nickel sulfide, belonging to the pentlandite group, occurring as small grains embedded in rock.

## Characteristics Sugakiite is a mineral from the pentlandite group, being a copper, iron, and nickel sulfide. It occurs as very small, anhedral (not exhibiting external crystalline forms) grains, usually not exceeding 100 micrometers in size. These grains are embedded in other minerals, most commonly troilite. Due to its microcrystalline nature, visual features are difficult to observe without specialized equipment, such as a reflected light microscope. ## Physical Properties This mineral is opaque and exhibits a metallic luster. Its hardness and density have not been precisely measured due to the small size and mode of occurrence of the grains. The fracture is uneven. ## Colors and Varieties Sugakiite has a characteristic reddish or yellowish-red color. No varieties of this mineral are distinguished. ## History and Name Sugakiite was first described in 1984 by A. Kitakaze and A. Sugaki. The mineral's name honors Professor Asahiko Sugaki (1913–1995), a Japanese mineralogist and petrologist from Tohoku University, in recognition of his contribution to ore mineralogy. The mineral and its name were approved by the International Mineralogical Association (IMA) in 1982 (IMA1982-088). ## Applications Sugakiite has no industrial or commercial applications. Its significance is purely scientific and collectible, although due to its rarity and microscopic size, it is primarily of interest to specialized collectors of rare minerals.

Properties

Luster
Metallic
Density
0
Fracture
Irregular/Uneven
Transparency
Opaque
Crystal system
Tetragonal

Diagnostic features

## Identification Identification of sugakiite is possible almost exclusively using advanced laboratory techniques, such as electron probe microanalysis (EPMA) and X-ray diffraction (XRD). In reflected light microscopy, sugakiite stands out with its yellowish-red color against co-occurring sulfides, such as troilite or pentlandite. ## Distinguishing from Similar Minerals Sugakiite can be confused with other sulfides of similar color, such as chalcopyrite, pentlandite, or cubanite. Definitive differentiation requires chemical composition analysis, as all these minerals can co-occur in the same parageneses. Sugakiite is distinguished by a specific ratio of copper, iron, and nickel. ## Crystal Forms This mineral forms exclusively anhedral, irregular grains, most often in intergrowths with other sulfides. No well-formed crystals have been observed.

Geological environment

## Genesis Sugakiite is a mineral of magmatic origin. It forms as a result of crystallization from a sulfide melt within ultramafic (very rich in magnesium and iron) intrusions. In its type locality (Horoman), it is associated with peridotites. ## Mineral Associations This mineral occurs in close association with other sulfides. It is most commonly accompanied by troilite (a variety of pyrrhotite), pentlandite, chalcopyrite, and heazlewoodite. It also co-occurs with chromite. ## Localities The only confirmed and thoroughly described locality of sugakiite in the world is its type locality – the Horoman mine within the Horoman peridotite intrusion, in Hokkaido Prefecture, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to the microscopic nature of sugakiite, the collectible value of a specimen is not assessed based on typical criteria such as size or crystal form. The most valuable are rock samples (polished sections or thin sections) from the type locality, in which the presence of sugakiite has been analytically confirmed. The value of a specimen increases with the richness of the mineral association and the clarity of the relationships between individual minerals under the microscope. ## Popular Localities The only source of specimens is the Horoman mine in Japan. Material from this locality is extremely rare on the collector's market.

Care and storage

## Cleaning Specimens containing sugakiite, which are typically rock fragments, do not require specialized cleaning. If necessary, they can be rinsed with distilled water and dried with a soft cloth or left to air dry. Mechanical cleaning, which could damage the microscopic mineral grains, should be avoided. ## What to Avoid As a sulfide, sugakiite can be sensitive to acids and strong oxidizing agents. Contact with household and laboratory chemicals should be avoided. Prolonged exposure to moisture can lead to slow oxidation. ## Storage Specimens with sugakiite should be stored in stable conditions, away from extreme temperatures and humidity. It is best to keep them in closed display boxes to protect them from dust and mechanical damage.

External references

Sources

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