This former nickel mine is the type locality for heazlewoodite and hellyerite, and the source of many rare minerals, including awaruite, dypingite, retgersite, reevesite, theophrastite and several new, unnamed minerals.
In the past, collectors concentrated mainly on three minerals: what they labeled green zaratite, blue hellyerite, and the massive sulfide heazlewoodite. The Lord Brassey mine is the type locality for the latter two minerals.
The primary mineralization consists of nickel sulfides (pentlandite and heazlewoodite) with minor Ni-Fe alloy (awaruite) intergrown with grains of magnetite and various silicates (Williams, 1958).
Andradite is relatively abundant in serpentinized mafic and ultamafic rocks in the Lord Brassey mine, as very fine-grained, pale green masses of granular crystals to a few micrometers in size, in shear planes in serpentine (Ford, 1970), and commonly associated with heazlewoodite. Analyses (X-ray fluorescence and wet chemical) show about 1.9 weight % [Cr.sub.2][O.sub.3] and 0.9 weight % [H.sub.2]O, indicating a hydrous chromian andradite (Ford, 1970).
X-ray powder diffraction analyses of a sliced silvery mass collected by Peter Andersen gave a mixture of heazlewoodite, magnetite and a nickel-iron phase.
The bronzy yellow sulfide, heazlewoodite, was first recorded from this locality.
Magnetite occurs as interstitial filling between heazlewoodite grains and is also quite common throughout the host rocks, sometimes in massive form.
Millerite was reported by Williams (1958) as fine inclusions in heazlewoodite and as an alteration product of pentlandite.
Pale bronze-yellow pentlandite occurs as intergrowths with heazlewoodite in the serpentine, but is usually subordinate.
Heazlewoodite was considered by Ramdohr (1969) to be of probable hydrothermal origin, perhaps by oxidation of pentlandite (a reaction not supported by textures seen in this study).