Cadmium

Chemical formula: Cd

Native cadmium is a rare native element with a metallic luster, occurring as small, hexagonal plates and flakes.

## Characteristics Native cadmium is a naturally occurring, crystalline form of the element cadmium. It belongs to the rare group of native elements. It usually occurs as very small, hexagonal plates or flakes, rarely forming larger aggregates. Its surface is typically shiny, with a metallic appearance, often covered with a tarnish that can alter its color. ## Physical Properties This mineral is soft and malleable, meaning it can be easily scratched and deformed. It is characterized by high density and a metallic luster. It is opaque. Its Mohs hardness is 1-2, and its density is approximately 8.64 g/cm³. ## Colors and Varieties Fresh surfaces of native cadmium have a tin-white or silvery-white color with a slight bluish tint. When exposed to air, it quickly tarnishes and becomes covered with a gray or black oxide film. No distinct varieties are recognized. ## History and Name The mineral's name comes from the Greek word "kadmeia" (καδμεία), an old name for calamine (zinc ore), with which it often co-occurs. The element cadmium was discovered in 1817 by the German chemist Friedrich Stromeyer. As a mineral, it was first described much later, after its natural occurrences were found. ## Applications Native cadmium has no direct industrial application due to its extreme rarity. It is solely an object of scientific and collector interest. Commercial cadmium, used in batteries and alloys, among other things, is obtained as a byproduct of zinc, lead, and copper smelting.

Properties

Mohs hardness: 1-2
Color: Tin-white with bluish tint
Luster: Metallic
Streak: Gray
Density: 8.65
Cleavage: Perfect on {0001}
Fracture: Hackly
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Native cadmium is identified by its metallic luster, silvery-white color (on a fresh surface), high density, and extreme softness (it can be scratched with a fingernail). Its characteristic occurrence as small, hexagonal plates or flakes is also diagnostic. ## Distinguishing from Similar Minerals It can be confused with other native elements such as tin, lead, or zinc. It differs from native tin by a slightly different crystal habit. It is harder than lead (lead has a hardness of 1.5) and lighter. Native zinc is even rarer and has similar properties, but a definitive distinction often requires chemical analysis (EDS). ## Crystal Forms It crystallizes in the hexagonal system. Most often, it forms very small, thin, six-sided plates and lamellae. Less commonly, it is found as granular aggregates or as coatings on other minerals.

Geological environment

## Genesis Native cadmium is a low-temperature hydrothermal mineral. It forms in the oxidation zones of ore deposits, mainly zinc. It can also form in active volcanic environments, where it precipitates from gases (fumaroles), as observed at Kudryavy volcano. ## Mineral Associations It most commonly co-occurs with zinc minerals such as sphalerite and smithsonite. In volcanic environments, it is accompanied by other sublimated minerals, e.g., greenockite (cadmium sulfide). ## Localities Confirmed occurrences of native cadmium are few. The most important localities are Ust'-Khanninskoye in Yakutia (Russia), where it was found as plates in hydrothermal veins, and Kudryavy volcano on the Kuril Islands, where it is currently forming from volcanic gases. It is also known from the Enterprise mine in the Keno Hill area of the Canadian Yukon.

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of a specimen primarily depends on the size and development of the crystals, which is extremely rare. Even microscopic but well-formed hexagonal plates are highly valued. Association with other minerals, forming an aesthetic composition on the rock matrix, is also important. Due to its rarity, every documented specimen has significant scientific and collector value. ## Popular Localities The most known and valued specimens come from Russia, especially from Yakutia (Ust'-Khanninskoye) and from Kudryavy volcano on the Kuril Islands. Material from these localities is considered classic for this mineral.

Care and storage

## Cleaning Native cadmium specimens are extremely delicate and rare, so cleaning them is generally not recommended. If absolutely necessary, a very soft brush can be used to remove loose dust. Avoid contact with water and any chemicals. ## What to Avoid Cadmium is sensitive to moisture and atmospheric oxygen, which causes it to tarnish and develop a dark film. Contact with acids and other chemicals must be strictly avoided. Due to its softness, it is very susceptible to scratching. Cadmium and its compounds are toxic – avoid inhaling dust and wash hands after any contact with the mineral. ## Storage Specimens should be stored in airtight, dry containers or "perky boxes" to limit exposure to air and moisture. It is best to keep them in stable conditions, away from heat sources and direct sunlight. Due to its toxicity, it should be stored out of reach of children and pets.