A gold-silver mine started spring 1989. An underground working owned by the Cheni Gold Mines, Inc. Includes the Amethyst Gold Breccia, Cliff Creek and Duke's Ridge deposits.

Epithermal gold-silver mineralization at the Lawyers mine occurs in quartz vein stockwork bodies and chalcedony breccia zones which appear to be controlled by fracture systems related to graben margins. Three deposits have been discovered to date and are known as the AGB zone (Amethyst Gold Breccia zone), the Cliff Creek zone, and the Duke Ridge zone. The Cliff Creek zone, a parallel zone which lies approximately 1931 metres to the west of the AGB zone, extends for a strike length of at least 1609 metres. The Duke Ridge zone extends for at least 1219 metres, and is a cross structure between the Cliff Creek and AGB zones.

The AGB zone strikes north and extends for at least 548 metres with widths of up to 12 metres. Mineralization consists predominantly of native gold, native silver, electrum and acanthite with minor chalcopyrite, sphalerite and galena, in a gangue of chalcedony and quartz, and minor calcite. It occurs as fracture fillings in stockwork veins as well as in the matrix within breccia zones and is controlled by a north and north-northeast trending fracture system which dips steeply to the west. Potassium-argon dating of adularia from vein selvages yielded a mineralization age date of 180 +/- 6 Ma (Middle Jurassic) (Fieldwork 1985). Geometrically, the resulting veins and breccia zones crosscut the stratigraphy, emerge from the older footwall quartz andesites and pass through the younger overlying trachyandesite sequence. At lower levels within the quartz andesite, the AGB zone appears as a single distinct vein system, whereas in the upper levels, the system splays into two prominent zones. In cross-section, the whole system resembles a "Y" configuration.

Within the breccia zones are at least four periods of chalcedony and quartz deposition. The colour of chalcedony varies from white to cream, green, grey to dark grey, red and opaque brown. Quartz, amethyst, and to a minor extent calcite, are present in the centres of veins and breccia zones, representing the last stages of open-space filling. Chalcedony breccias and stockwork veins are often rebrecciated in areas cut and offset by postmineral faults, such as the D1 fault. The matrix in the rebrecciated chalcedony breccias is predominantly limonite, various clay minerals, and to minor extent hematite.

Chalcedony breccia zones and veins in quartz andesite are bordered by bleaching and silicification of wallrock with quartz and chalcedony veinlets and hematite. Intensity of chalcedony veining and microbreccias increases with more extensive bleaching, silicification and argillization. Chalcedony matrix within breccia zones and veinlets is impregnated with hematite and various other iron oxide minerals, including minor jasper. A propylitic zone, consisting of chlorite, minor epidote and calcite veinlets, is peripheral to the zone of bleaching and silicification. Sericite is present only in minor amounts within the breccia zones and as narrow selvages.

At the Duke Ridge and Cliff Creek zones, chalcedony breccia zones are similar to those in the AGB zone. However, the breccia zones are generally better defined with sharper vein boundaries and at least four periods of chalcedony and quartz deposition are present. Near the surface and near postmineral faults, the breccia zones are broken up, with wallrock fragments completely altered to clay. On Duke Ridge, the breccia zones appear to be refracted along the contact between andesite crystal tuffs and a fine grained tuff member. Breccia zones, as in the case of the AGB zone, do not form strong and well-defined zones in the fine-grained tuffs.

In the Cliff Creek and Duke Ridge zones, chalcedony breccia zones and stockwork veins are associated with pervasive argillic alteration. The alteration consists of various clay minerals with or without limonite, goethite, hematite, and manganese oxides and varies in thickness from about 5 to 50 metres. Propylitic alteration with chlorite, epidote, and to a minor extent calcite, is present peripheral to the argillic zone. Superimposed on these is a supergene alteration zone of various clays and limonite up to 30 metres deep. Gold and silver values are generally low within supergene altered areas.

A new vein zone was discovered within the area of intersection between the Cliff Creek and Duke Ridge structures. Trenching exposed a 200 metre strike length of strong veining with sampling yielding 4.79 grams per tonne gold and 145.34 grams per tonne silver across 1 metre (George Cross News Letter No. 171 (September 5), 1990).

Examination of polished and polished thin sections of chalcedony-quartz breccia samples from both the AGB and Duke Ridge zones reveal hypogene and supergene types of mineralization. In both types, the various ore minerals occur in microfractures, vugs, and grain and crystal boundaries of non-sulphide and non-metal vein constituents. The hypogene type is characterized by acanthite, native gold, electrum with minor sphalerite, galena, and chalcopyrite, with up to 5 per cent pyrite. In places, acanthite projects inward from the walls of vugs with calcite in the interstices. The main gangue vein minerals are banded chalcedony and quartz, and minor barite. Calcite and barite occur in centres of veins and as matrix in breccia.

The supergene type is made up of acanthite, native gold, and electrum with hematite, lepidocrocite, and goethite disseminated through the gangue constituents, and pseudomorphic after pyrite. Acanthite occurs in limonitic cavities or boxworks from which sphalerite, chalcopyrite and galena were probably leached out by acidic solution derived from the breakdown of pyrite.

Cheni Resources Inc. completed reclamation of the Lawyers mine in September 1998.

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Mineral List

12 valid minerals.