Heazlewoodite

Chemical formula: Ni<sub>₃</sub>S<sub>₂</sub>

Heazlewoodite is a metallic, brownish-yellow nickel sulfide, found in serpentinites and ultramafic igneous rocks.

## Characteristics Heazlewoodite is a nickel sulfide with a metallic appearance. It typically forms granular or massive aggregates, embedded in the host rock. It is rarely observed in the form of well-developed crystals. Its most characteristic feature is its color – from light brownish-yellow to coppery brown, which exhibits a strong, metallic luster on fresh fracture surfaces. Over time, it may tarnish or develop a patina. ## Physical Properties This mineral is relatively hard, with a Mohs hardness of 4. It is opaque and quite dense, with a specific gravity of approximately 5.82 g/cm³. It does not exhibit cleavage, and its fracture is uneven. It possesses a strong, metallic luster. ## Colors and Varieties Heazlewoodite is a mineral of uniform coloration. Its color ranges from light yellow, through brownish-yellow, to a copper-like brown hue. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral's name comes from its discovery locality – the Heazlewood mine in Tasmania (Australia). It was first described by William Frederick Petterd in 1896. The name honors both the location and the Heazlewood family, who were significant in the history of this mining region. ## Uses Heazlewoodite, when occurring in sufficiently large concentrations, can be a minor source of nickel. However, its primary role is as an indicator mineral in the exploration for nickel sulfide and platinum-group element deposits. For collectors, it is mainly interesting as a component of rare mineral parageneses from ultramafic rocks.

Properties

Mohs hardness: 4
Color: Light bronze or brass yellow
Luster: Metallic
Streak: Light bronze
Density: 5.82
Cleavage: None
Fracture: Hackly
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Heazlewoodite is recognized by its characteristic brownish-yellow color, strong metallic luster on a fresh surface, and occurrence in serpentinites or other ultramafic rocks. It is opaque and non-magnetic. Its hardness (4 on the Mohs scale) is helpful in distinguishing it from softer sulfides. ## Distinguishing from Similar Minerals Heazlewoodite is sometimes confused with pentlandite, which has a very similar color and luster. However, pentlandite usually exhibits distinct parting. It is distinguished from chalcopyrite by the absence of brassy-yellow and greenish hues, and from pyrrhotite by the lack of magnetic properties and a lighter color. Bornite, in contrast, is characterized by a variegated, blue-violet iridescence, which heazlewoodite does not possess. ## Crystal Forms Well-formed heazlewoodite crystals are extremely rare. It usually occurs as small, irregular grains, granular aggregates, or as massive infillings in the host rock.

Geological environment

## Genesis Heazlewoodite is a mineral typical of serpentinized peridotites and dunites. It forms as a result of low-temperature hydrothermal processes or during the serpentinization of ultramafic rocks, when nickel released from olivines reacts with sulfur. It can also crystallize directly from nickel-rich sulfide magmas. ## Mineral Associations This mineral often co-occurs with other nickel and iron sulfides. Its typical associated minerals include pentlandite, awaruite, millerite, as well as magnetite, chromite, and minerals from the serpentine group (antigorite, lizardite, chrysotile). ## Localities Key heazlewoodite localities worldwide include its type locality in Heazlewood, Tasmania (Australia), as well as deposits in the Sudbury region in Ontario and Asbestos in Quebec (Canada), in the Ural Mountains (Russia), in Kraubath (Austria), and in many places in California and Oregon (USA), where it occurs in serpentinites.

Rarity

Not very common

For collectors

## Quality Criteria Heazlewoodite's collector appeal is not so much related to the form of individual crystals, but rather to the richness and aesthetics of the entire specimen. The most prized samples are those in which heazlewoodite forms distinct, lustrous aggregates of intense, brownish-yellow color, contrasting with the dark host rock (serpentinite). Specimens with clearly visible mineral associations, such as acicular millerite or silvery awaruite, are also highly valued. ## Popular Localities Collector-grade specimens come from classic localities for this mineral. Those from the Zeehan and Heazlewood district in Tasmania are particularly valued. Good quality material, often in association with other rare minerals, is also supplied by some mines in Quebec (Canada) and California (USA).

Care and storage

## Cleaning Heazlewoodite specimens should only be dry-cleaned, using a soft brush to remove dust. Contact with water, and especially with chemicals, can lead to oxidation and tarnishing of its metallic surface. ## What to Avoid All acids and cleaning agents should be strictly avoided. The mineral is sensitive to moisture, which accelerates oxidation processes. It should not be heated or exposed to prolonged intense light. ## Storage It is recommended to store specimens in a dry place, preferably in closed display boxes or cabinets with a desiccant, to protect the metallic luster from tarnishing. Avoid storage in damp basements.