Neyite

Chemical formula: Ag₁+₂Cu₁+₆Pb₂+₂₅Bi₃+₂₆S₂-₆₈

A rare sulfide of lead, bismuth, silver, and copper, forming acicular or fibrous crystals with a metallic luster.

## Characteristics Neyite is a complex sulfosalt with the chemical formula Ag₂Cu₆Pb₂₅Bi₂₆S₆₈. It forms elongated, platy or acicular crystals, which rarely occur individually. It typically forms tangled, fibrous masses or radial aggregates. The mineral is opaque, has a lead-gray to grayish-black color, and a characteristic metallic luster. Over time, its surface may become covered with a darker tarnish. ## Physical Properties Neyite is a relatively soft mineral with a hardness of 2.5-3 on the Mohs scale. It has a high density, approximately 7.03 g/cm³. The luster is strongly metallic, and the mineral is completely opaque. ## Colors and Varieties The mineral occurs in shades of lead-gray, often with a black tint. No color or commercial varieties are distinguished. ## History and Name Neyite was described in 1969 by A. D. Drummond, J. Trotter, R. M. Thompson, and J. A. Gower. The mineral is named in honor of Charles S. Ney (1914–1991), a Canadian geologist who conducted research in the area of the mineral's type locality. ## Uses Due to its rarity, neyite has no industrial applications. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 2.5-3
Luster: Metallic
Streak: Black
Density: 7.03
Cleavage: Good on {100}
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Neyite can be initially recognized by its characteristic form – acicular or platy crystals forming radial or tangled aggregates. Other helpful identification features include its lead-gray color, strong metallic luster, high density, and low hardness. The streak is black. ## Distinguishing from Similar Minerals Visual distinction of neyite from other gray, metallic sulfosalts (e.g., cosalite, bismuthinite, aikinite) is extremely difficult and often impossible without advanced analysis. Similar minerals often have comparable appearance and physical properties. Only chemical analysis (e.g., EDS) or X-ray diffraction (XRD) allows for certain identification. ## Crystal Forms Crystals are elongated along one axis, taking the form of needles, plates, or fibers. They almost always occur as aggregates – radial, tangled, or fibrous masses.

Geological environment

## Genesis Neyite is a hydrothermal mineral. It forms in ore veins under medium-temperature conditions. ## Mineral Associations It most commonly co-occurs with quartz, as well as with other sulfides and sulfosalts, such as galena, sphalerite, pyrite, cosalite, aikinite, and galenobismutite. ## Localities The most important and also the type locality for neyite is the Alice Arm area (Lime Creek quartz vein) in British Columbia, Canada. This mineral has also been found in Moctezuma, Sonora, Mexico, as well as in several locations in Japan (Ohtani mine) and Sweden (Vena area).

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued neyite specimens are those that exhibit well-formed, undamaged crystals in the form of distinct, radial aggregates, preferably set on a contrasting matrix (usually white quartz). The size and richness of the aggregate significantly increase the specimen's value. ## Popular Localities Specimens from the type locality in British Columbia, Canada, are considered classic and most sought after by collectors. They serve as the standard for this mineral.

Care and storage

## Cleaning Neyite specimens should be cleaned very carefully, preferably dry, using a soft brush to remove dust. Contact with water should be avoided, as it can accelerate the oxidation process. If wet cleaning is absolutely necessary, distilled water should be used, and the specimen should be thoroughly dried immediately. ## What to Avoid The mineral is sensitive to moisture and chemical reagents, especially acids. It is soft and brittle, so it should be protected from impacts, scratching, and vibrations (e.g., in ultrasonic cleaners). ## Storage It is recommended to store specimens in a dry place, preferably in closed, airtight containers or display cases, to limit contact with air and moisture, which will slow down the oxidation process and the formation of tarnish.

Sources

IMA Mineral List (CNMNC)