Graemite

Chemical formula: Cu₂+Te₄+O₃·H₂O

A very rare copper tellurite, forming intensely green, acicular crystals, prized by collectors of rare minerals.

## Characteristics Graemite is a hydrated copper tellurite, known for forming microscopic yet perfectly formed crystals. Typical specimens consist of small, slender prismatic or acicular crystals, which often form radial or divergent aggregates and crusts. Its most characteristic features are its intense, emerald-green to dark-green color and a strong, almost adamantine luster, which distinguishes it from other secondary copper minerals. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3-4. It is characterized by a vitreous to adamantine luster and is transparent to translucent. Its density is approximately 4.19 g/cm³, which is a relatively high value for a secondary mineral. ## Colors and Varieties Graemite occurs in uniform, vivid shades of green, from emerald to very dark, almost black-green. No named color varieties or trade names are distinguished for it. ## History and Name The mineral is named in honor of Richard H. Graeme III (born 1936), a mining engineer and collector from Bisbee, Arizona, who made significant contributions to preserving the mineralogical heritage of that region. Graemite was first described in 1975 by S.A. Williams and P.J. Matter III based on material from the Cole shaft in the Bisbee mine, Cochise County, Arizona, USA. ## Uses Due to its extreme rarity and small crystal size, graemite has no industrial applications. It is of purely scientific importance and is a highly valued collector's item.

Properties

Mohs hardness: 3-4
Luster: Vitreous to Adamantine
Streak: Light green
Density: 4.19
Cleavage: Perfect on {010} and {100}
Fracture: Conchoidal
Transparency: Transparent to Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Key features for identifying graemite are its intense emerald-green color, strong luster (often adamantine), characteristic acicular crystal habit forming radial aggregates, and paragenesis with other rare tellurites and tellurates. ## Distinguishing from Similar Minerals Graemite is sometimes confused with other green, secondary copper minerals. It differs from malachite by its lack of reaction with hydrochloric acid and a much stronger luster. It differs from brochantite by its crystal habit and often more intense color. Teineite, another copper tellurite from the same locality, typically has a blue color. ## Crystal Forms Graemite forms slender, elongated prismatic and acicular crystals. They most often occur as divergent, radial, or fan-shaped aggregates, as well as thin crusts on the host rock.

Geological environment

## Genesis It is a secondary mineral, forming in the oxidation zones of hydrothermal ore deposits rich in copper and tellurium. It forms as a result of weathering and alteration of primary tellurium minerals (such as native tellurium) and copper sulfides under conditions of low temperatures and pressures. ## Mineral Associations Graemite often co-occurs with other rare tellurium minerals, especially at its type locality. Its typical associations include: teineite, spiroffite, poughite, xocomecatlite, as well as cuprite, native copper, and native tellurium. ## Localities The most important and historical occurrence of graemite is its type locality – the Cole shaft in Bisbee, Arizona, USA. It is also known from several other places in the world, including the Bambolla mine in Moctezuma, Sonora, Mexico. However, specimens from Bisbee remain the standard for this species.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued graemite specimens are those with sharply terminated, lustrous microcrystals of an intense, emerald color, forming aesthetic, radial groups on a contrasting matrix. Due to its rarity, even well-defined microminerals achieve significant value. Crystal size, luster, and color purity are key evaluation factors. ## Popular Localities By far the most sought-after and classic specimens come from the historic locality in Bisbee, Arizona. Material from this location is considered the best in the world and serves as a benchmark for collectors of rare minerals and those specializing in tellurium minerals.

Care and storage

## Cleaning Graemite specimens should be cleaned very carefully, using only distilled water and a soft brush to remove dust. Ultrasonic cleaners should not be used, as they could damage the delicate crystals. ## What to Avoid The mineral is sensitive to high temperatures, which can lead to its dehydration (loss of water) and structural damage. Contact with acids and strong chemicals should be avoided. Due to its low hardness, it is susceptible to scratches and mechanical damage. ## Storage It is recommended to store specimens in sealed mineralogical boxes that protect against dust, light, and damage. Avoid sudden changes in temperature and humidity.

Sources

IMA Mineral List (CNMNC)