Arsenopyrite Gold Pyrite
Virtual Museum ID: 19-AME161
Gold and Iron
Gold is a valuable, highly prized mineral used in everything from jewellery to electronics and dentistry. Gold is desirable due to its special properties, such as malleability and resistance to tarnishing. Gold is commonly microscopic or embedded within or around sulphide grains. Free visible gold occurs as disseminated grains, or rarely as crystals. In its natural mineral form, gold is commonly alloyed with silver. Gold is distinguishable by its characteristic golden yellow colour and extreme heaviness.
Pyrite is a common iron sulphide mineral found in many different geological settings. It has a brassy-yellow metallic colour that has caused many people to mistake it for gold, giving it the name “Fool’s gold”. Pyrite and gold can be quite easily distinguished from one another: pyrite is less yellow and much lighter and harder than gold, which can be scratched with a pocket knife. Pyrite often forms perfect cubes, which can grow to quite large sizes, because of its crystal structure. The word pyrite comes from the Greek word ‘pyr’ meaning fire, because it will spark if hit with other metal or stone objects.
Arsenopyrite is a sulphide similar to pyrite but contains arsenic as well as iron. It has a more silvery colour than pyrite and forms blocky or tabular crystals rather than cubes. Its surface often has striations, or stripes. Arsenopyrite is one of the main ore minerals for arsenic, which is used in wood preservatives and insecticides. In its oxide forms, arsenic is toxic so it is not widely used.
This sample is from the Cousin Jack property near Tulameen, about 25 km northwest of Princeton in southern BC.
Mineralization at Cousin Jack is in quartz-carbonate veins that contain varying amounts of pyrite, arsenopyrite, sphalerite, galena, gold and silver. This sample contains pale arsenopyrite, yellow pyrite and small amounts of gold.
The area has been prospected and staked since the early 1900s, and even explored with short test adits, but so far no major deposits have been found or mined on the Cousin Jack properties.
The information listed below relates to the current holding location or collection that the sample is from, and whether the item is viewable at that location or is part of a private collection. Coordinates are given as guides, and we remind you that collecting specimens from these locations is not allowed. Caution is advised visiting such sites and Below BC assumes no responsibility for any injuries or trespassing charges that may occur as a result of the viewer entering these sites.
Original Collection:Association for Mineral Exploration (AME)
Virtual Museum ID:19-AME161
Date Added to VM:2018-02-15
Sample Origin:Boulder Mountain, Tulameen, B.C.
Specific Site:Cousin Jack
Datum:10 (NAD 83)
Primary Features:Arsenopyrite Gold Pyrite
Primary Mineral Formula:FeS2, Au, FeAsS
Primary Category:sulphide native element
Advanced Geological Information
The following section provides geological data relating to the specimen or the site it was collected from, when available. Information has been obtained from various sources including private and government datasets but may not be up to date. Any geological time periods or ages listed often relate to the primary geology of the area, and may not be the actual date of an event such as mineral formation.
Geological Period:Upper Triassic
Stratigraphic Age:145 to 163.5 Million Years Ago
The Cousin Jack prospect outcrops along the northeast flank of Boulder Mountain, 2 to 3 kilometres north of Lockie (Boulder) Creek and 7 to 8 kilometres north-northwest of Tulameen.
The northeastern slopes of Boulder Mountain are underlain by andesitic to dacitic flows and pyroclastic volcanic rocks of the Upper Triassic Nicola Group. These rocks strike north, dip west and are regionally metamorphosed up to greenschist facies. A weak to moderately developed foliation dips 10 to 20 degrees west. The volcanics are flanked to the east by an elongate body of granodiorite of Late Triassic to Early Jurassic age outcropping along Otter Lake.
A zone of concordant to discordant quartz-carbonate veins occurs in andesite (greenstone) over a north-south distance of 1200 metres. Individual veins strike north for lengths of up to 380 metres and dip shallow to steeply west. They vary from 2 centimetres to 3 metres wide, but average less than 0.5 metre in width.
The andesite is sheared and hydrothermally altered in this zone of veining. The rock exhibits pervasive quartz-sericite-argillic alteration in the hangingwall and well-developed propylitic alteration in the footwall of steeply west dipping veins.
The veins and surrounding wallrock are variably mineralized with sphalerite, pyrite, galena and chalcopyrite. The veins are frequently pyritic and are sometimes mineralized with polymetallic massive sulphides. Such vein-hosted sulphides are massive to weakly interbanded with quartz. The locally convolute banding suggests an epithermal origin (Assessment Report 15315). Pyrite, galena and sphalerite are present in silicified wallrock as stringers and bands.
Surface sampling suggests the veins average 1 to 3 per cent combined lead and zinc, 0.2 per cent copper, 6.9 grams per tonne silver and 6.9 grams per tonne gold (Assessment Report 15315, page 21). A chip sample across a 1-metre wide vein with sphalerite and galena assayed 1.22 per cent lead, 12.49 per cent zinc, 0.09 per cent copper, 5.79 grams per tonne gold, and 20 grams per tonne silver (Assessment Report 13396, assay certificate, sample 6588). A chip sample taken across 0.9 metre of siliceous and pyritic andesite yielded 0.807 per cent lead, 7.666 per cent zinc, 0.186 per cent copper, 2 grams per tonne gold and 12.9 grams per tonne silver (Assessment Report 13396, assay certificate, sample 54287). Assays from diamond drilling ranged up to 1.1 grams per tonne gold, 26.4 grams per tonne silver, 1.90 per cent lead and 4.11 per cent zinc (Assessment Report 15993, page 7). The highest gold and silver values were found with highest lead and zinc values in siliceous andesite with minor carbonate.
This prospect was explored as early as 1901. Boulder Mining Company Ltd. conducted 98 metres of tunnelling in several adits between 1903 an 1905. The property was periodically assessed by several operators with minor development between 1922 and 1966. By 1971, Gold River Mines Ltd. had commenced a program of soil sampling and trenching, which culminated in the drilling of 33 diamond-drill holes totalling 1768 metres in 1972 and 1973. Since then, the deposit has been geophysically surveyed, trenched, mapped and sampled by various operators between 1980 and 1986. This work was followed with the drilling of 12 holes totalling 662 metres by Abermin Corporation in 1987.