Orthocuproplatinum

Chemical formula: Pt<sub>₃</sub>Cu

Orthocuproplatinum is a natural alloy of platinum and copper, forming small, metallic grains and flakes.

## Characteristics Orthocuproplatinum is a rare mineral from the native elements group, being a natural alloy of platinum and copper. It occurs as small, irregular grains, flakes, or rounded nuggets, usually not exceeding a few millimeters in size. Due to its composition, it has a metallic appearance and is opaque. ## Physical Properties This mineral is characterized by high density, typical for platinum alloys. It is a ductile and malleable material. The luster is strongly metallic, and the streak color is dark gray. ## Colors and Varieties Orthocuproplatinum has a color ranging from silvery-white to steel-gray, often with a slight pinkish or yellowish tint. Over time, it may develop a dull patina. No distinct varieties of this mineral are recognized. ## History and Name The name "orthocuproplatinum" refers to its chemical composition (copper - Latin *cuprum*, platinum) and its orthorhombic crystal structure. It was described as a new mineral in 1991 based on material from the Kondyor massif in Russia. ## Uses Due to its rarity and small grain sizes, orthocuproplatinum has no direct industrial application. However, it constitutes a minor source of platinum in deposits where it occurs. It is primarily valued by collectors specializing in platinum group minerals.

Properties

Mohs hardness: 4-5
Luster: Metallic
Streak: Dark gray
Density: 14.5
Cleavage: None
Fracture: Hackly
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of orthocuproplatinum is based on its silvery-white or steel-gray color with metallic luster, high density, and magnetic properties (or lack thereof). It occurs as small, irregular grains or flakes. Final confirmation requires advanced methods such as chemical composition analysis (EDS) and X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other platinum group minerals, such as native platinum, tetraferroplatinum, or cuproplatinum. Native platinum is usually more silvery and less dense. Cuproplatinum has a similar composition but crystallizes in the isometric system. Distinguishing these minerals without specialized equipment is practically impossible. ## Crystal Forms Crystals are extremely rare and microscopic. Most often, it occurs in the form of irregular, anhedral (unformed) grains, rounded nuggets, and thin flakes, often intergrown with other platinum group minerals.

Geological environment

## Genesis Orthocuproplatinum is a mineral of magmatic origin. It forms in ultramafic, alkalized magmatic complexes, such as concentrically zoned Alaskan-type massifs (e.g., the Kondyor massif). It crystallizes from magma rich in platinum and copper under high-temperature conditions. ## Mineral Associations It most commonly co-occurs with other platinum group minerals (PGM), such as native platinum, cuproplatinum, tetraferroplatinum, as well as chromite, magnetite, olivine, and pyroxenes. ## Localities The most important and type locality is the Kondyor massif in the Aldan Shield (Khabarovsk Krai, Russia), from which the best specimens originate. It has also been reported in other ultramafic massifs in Siberia (e.g., Feklistov) and in Colombia (Chocó Department).

Rarity

Very rare

For collectors

## Quality Criteria The most valuable specimens for collectors are those with well-defined, visible-to-the-naked-eye grains or flakes of orthocuproplatinum, especially if they contrast with the surrounding rock (matrix). Exceptionally rare, partially formed crystals command the highest prices. Nugget size is a key factor influencing value. ## Popular Localities Undoubtedly, the most prized and sought-after specimens come from the Kondyor massif in Russia. Material from this locality is considered the global standard for this mineral.

Care and storage

## Cleaning Orthocuproplatinum specimens are usually not chemically cleaned to avoid damaging the natural patina or co-occurring minerals. If necessary, compressed air can be used to remove dust, or they can be gently rinsed with distilled water and dried. ## What to Avoid Avoid contact with acids and strong chemicals, which can react with the copper in the alloy. Prolonged exposure to humid air can accelerate the patination process. ## Storage It is recommended to store specimens in a dry place, preferably in closed display boxes or cabinets, to protect them from dust and contaminants. As it is a stable mineral, it does not require special temperature or lighting conditions.

Sources

IMA Mineral List (CNMNC)