The Tax occurrence is located on an east- facing slope, north of Fifteen Mile Creek and approximately 1.2 kilometres west of the Coquihalla River.
The Coquihalla Serpentine Belt forms a narrow, elongate, north-northwest trending, steeply dipping unit separating supracrustal rocks of the Lower-Middle Jurassic Ladner Group to the east, from the Hozameen Complex in the west. Dark, highly sheared to massive serpentinite, of probable peridotite parentage, characterizes the belt. It also contains substantial amounts of highly altered gabbro-diabase rocks.
The eastern margin of the serpentine belt is sharply delineated by the Hozameen fault. The western boundary is also represented by a major fracture that appears to dip steeply east. This is termed the "West" Hozameen fault and the serpentinites in this vicinity contain highly sheared talcose rocks.
The "East" Hozameen fault separates the serpentinite from the Ladner Group metasediments. The Ladner Group is comprised of a thick section of complexly folded black slate, cherts and intercalated basalts.
The serpentinite, derived from dunite to peridotite, has a complex association with diorite intrusions, which occur as dike-like bodies within the ultramafics. The contacts are commonly a locus of shearing. Details of the unsheared contact indicate a gradational change in mineralogy over a few centimetres. Carbonate is a common constituent in such localities, and occurs as stringers or disseminations throughout the rock. Tabular to lenticular, unaltered, diorite blocks also occur in the serpentinite.
There are several narrow fault zones developed parallel to the north-northwest regional trend. Most faults developed along the diorite-serpentinite contact or the contact of the Coquihalla Serpentine Belt and the country rocks. It is thought that the consistency of the faulting indicates the mafic-ultramafic complex was emplaced as a solid state fault slice. Complex folding in the Ladner Group is not reflected in the ultramafic rocks so it appears the folding was prior to the ultramafic emplacement; thus, the ultramafics appear to be younger than the host rocks.
Mineralization in the ultramafics consists mainly of fine, nickel-bearing sulphides with coarse phenocrysts of pyrite. Samples of the serpentinite averaged 0.22 to 0.24 per cent nickel. Petrographic studies indicate the nickel mineralization consists of disseminated pentlandite with rare millerite and heazlewoodite. Secondary magnetite associated with the serpentinization is abundant. In areas that host a high percentage of magnetite, the nickel sulphides are less common. The serpentinite also hosts approximately 0.015 per cent cobalt in the form of wairauite, a rare, naturally occurring cobalt-iron alloy. Chromium spinels are also present in the serpentinite but due to the intimate association of chromium with other minerals, metallurgic studies indicated magnetic separation was not possible (Assessment Report 12340). Sulphides associated with the diorite and ultramafics include fine disseminations of pyrite, pyrrhotite and trace chalcopyrite.
In 1986, quartz-sulphide veins, which occur along the east contact of the serpentine belt, were examined. Samples yielded less than 0.068 gram per tonne gold (Assessment Report 16245).
In 1971, an airborne magnetic survey was completed on the area. The same year, Mountain Pass Mines completed a program of rock sampling on the area. In 1975, three diamond drill holes, totalling 105.0 metres, were completed on the area as the GWH claims. In 1976, Caroline Mines completed 4.0 line-kilometres of ground magnetic surveys on the area. During 1979 through 1984, Aquarius Resources completed programs of soil and rock sampling on the area as the Jessi claims. During 1981 through 1989, Border Resources completed programs of geological mapping, sampling and metallurgical testing on the area as the Tax claims.