Nullaginite

Chemical formula: Ni<sup>2+</sup><sub>2</sub>CO<sub>3</sub>(OH)<sub>2</sub>

Nullaginite is a rare, secondary nickel mineral, forming characteristic green, radial aggregates.

## Characteristics Nullaginite is a rare, secondary nickel carbonate. It occurs as small, spherical or hemispherical aggregates with a radial, fibrous internal structure. The individual "fibers" are actually elongated, bladed crystals. Its intense, emerald-green color is very characteristic and results from its high nickel content. ## Physical Properties Nullaginite crystals are very fine and form soft aggregates that are easily crushed between the fingers. The mineral exhibits strong pleochroism in shades of green. It has a luster described as silky or dull, depending on the form of occurrence. ## Colors and Varieties Nullaginite occurs exclusively in its characteristic emerald-green color. No color or commercial varieties are known. ## History and Name The mineral was first described in 1981 by E.H. Nickel and B.W. Robinson. Its name comes from its discovery locality – the Nullagine area in the Pilbara Craton, Western Australia. This is the only confirmed occurrence of this mineral (type locality). ## Uses Due to its extreme rarity and small size of occurrences, nullaginite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists.

Properties

Mohs hardness
1-2
Luster
Silky
Streak
Pale green
Density
3.45
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Translucent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic feature is the unique combination of emerald-green color, radial-fibrous aggregate form, and extreme softness. It reacts vigorously with acids, which is typical for carbonates. ## Distinguishing from Similar Minerals Nullaginite is sometimes confused with other secondary nickel minerals, such as bright green zaratite (which is amorphous and has a vitreous luster) or reevesite (which usually forms small, hexagonal plates). It differs from malachite by its much brighter, emerald shade of green (malachite is darker) and the lack of malachite's characteristic banding. ## Crystal Forms It forms spherical, rosette-like, and radial aggregates composed of fine, bladed or fibrous crystals, typically reaching up to 2 mm in diameter.

Geological environment

## Genesis Nullaginite is a secondary mineral, formed in the oxidation (weathering) zones of nickel ore deposits. It forms in voids and fissures of ultramafic rocks (e.g., serpentinites) as a result of the alteration of primary nickel sulfides, such as pentlandite. ## Mineral Associations It most often co-occurs with minerals from which it forms or which it accompanies in the oxidation zone. These are primarily reevesite, goethite, as well as relics of primary nickel and iron sulfides. ## Localities The only confirmed and described locality of nullaginite in the world is its type locality – the Otway serpentinite quarry in the Nullagine area, Pilbara region, Western Australia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a nullaginite specimen primarily depends on the size and completeness of the spherical aggregates, their number on the rock matrix, and the intensity and purity of the emerald-green color. Specimens with clearly formed, undamaged "spheres" or "rosettes" of nullaginite, contrasting with the dark host rock (serpentinite), are most highly valued. ## Popular Localities The only source of collector specimens is the type locality in Western Australia. Material from this location is extremely limited, and most specimens entered the market in the 1980s, shortly after the mineral's discovery.

Care and storage

## Cleaning Due to its extreme delicacy, nullaginite should practically not be cleaned mechanically or chemically. The aggregates are very soft and brittle. If absolutely necessary, a photographic air blower can be used to remove dust. ## What to Avoid Avoid contact with water, acids (it is a carbonate), chemical agents, and any tools. Even touch can damage the delicate, fibrous aggregates. It should not be heated or exposed to ultrasound. ## Storage Nullaginite specimens should be stored exclusively in sealed, padded "micromount" boxes to protect them from mechanical damage, dust, and humidity changes. It is not suitable for display outside of a specialized container.

Sources

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