Arsenopyrite Dolomite Gold Quartz

Specimen Summary

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 is not widely used.

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. Crystals of gold commonly form within or around quartz. In its natural mineral form, gold is commonly alloyed with silver. Gold is distinguishable by its characteristic golden yellow colour and extreme heaviness.

Quartz is the second most abundant mineral on Earth, occurring in many different types of rocks. Although usually clear or milky white in colour, quartz can be found in a variety of colours because of impurities in the crystal structure. Pure quartz is made up of silicon and oxygen only, but atoms of other elements, like iron or titanium, often make their way into the quartz crystal structure. Some varieties of quartz, like purple amethyst, are considered to be semi-precious gemstones and have been used since ancient times to make jewellery and decorative objects.

Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate. The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomitic rock type is dolostone.

This sample comes from the Whitewater Mountains near the post-producing Tulsequah Chief mine in northwestern BC, about 100 km southwest of Atlin, BC and 65 km northeast of Juneau, AK. It is made up mainly of dolomite and quartz with very fine arsenopyrite and gold.

The area is known to host several volcanogenic massive sulphide (VMS) type deposits. These are found in ancient volcanic arcs and usually form as pods or lenses of sulphide minerals like pyrite, chalcopyrite, sphalerite and galena. They can also contain gold and silver.

The nearby Tulsequah Chief mine was active from 1950 to 1957, and produced gold, silver, lead, zinc and copper from several sulphide lenses. The deposit contains large amounts of pyrite and lesser amounts of arsenopyrite, both of which are known for their role in generating acid rock drainage (ARD). As these minerals weather, their sulphide component is released and reacts with water to produce sulphuric acid, which is potentially harmful to the environment. The Tulsequah Chief mine ARD is currently being studied to assess its impact on salmon and other aquatic life in the nearby Tulsequah and Taku rivers.

Between 1950 and 1957, the mine produced over 580,000 tonnes of ore. This ore was processed with ore from the nearby Big Bull mine at the Polaris Taku mine facility. Average ore grades for the mines combined were 3.77 grams per tonne gold, 126.5 grams per tonne silver, 1.59 % copper, 1.54% lead and 7.0% zinc. The mine and surrounding area has been the focus of ongoing exploration work as recently as 2013.

Associated ores & minerals: Gold

Specimen Data

 

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.

Collection Details

Original Collection:

Association for Mineral Exploration (AME)

Sub Collection:

-

Collection ID:

AME-502

Virtual Museum ID:

19-AME502

Accessibility:

Date Added to VM:

2018-02-15

Location Information

Sample Origin:

Tulsequah, B.C.

Specific Site:

Whitewater Group

UTM Easting:

584422.4217

UTM Northing:

6502108.951

Datum:

08 (NAD 83)

Coordinate Accuracy:

Approximate

Specimen Details

VM Category:

Rock

Primary Features:

Arsenopyrite Dolomite Gold Quartz

Primary Mineral Formula:

FeAsS, MgCO3, Au, SiO2

Primary Category:

sulphide carbonate native element oxide

Secondary Features:

Greenstone

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 Formation:

Slocan Group

Geological Period:

Triassic

Stratigraphic Age:

Geological Belt:

Omineca

Geological Terrane:

Quesnel

Minfile ID:

082KSW033

Minfile Link:

https://minfile.gov.bc.ca/Summary.aspx?minfilno=082KSW033

Site Details:

The Whitewater occurrence, consisting of a major lode containing many orebodies, was covered by 24 Crown grants and fractions belonging to the Whitewater and Whitewater Deep groups. The underground workings on this lode lie on the west side of Whitewater Creek, 1 kilometre north of its confluence with the Kaslo River. A total of 471,063 tonnes of ore mined is recorded for this past producer spanning a period from 1892 to 1980. Records indicate about 108 tonnes silver, 54 kilograms gold, 23,132 tonnes zinc, 13,942 tonnes lead, 39 tonnes cadmium and 45 kilograms copper were recovered.

The Whitewater claim was located by J.C Eaton in 1892. In this same year 7.26 tonnes were shipped, the first shipment from this district. Property work and production were sporadic from this point to 1980, by various owners and lease holders. The Irene claim and perhaps others were added to the Whitewater Group in 1898 and the first concentrator was built on-site under the direction of the newly formed Whitewater Co. Ltd. Ground covering the Whitewater Deep group was acquired during this year by the Whitewater Deep Company and the No. 9 and 10 levels were tunnelled. A zinc-rich orebody was discovered below the No. 10 level but little or no work was done on it. Work was carried out independently on the Whitewater and Whitewater Deep groups until J. Retallack and associates acquired a lease on the Whitewater Deep group. At this time the workings were connected. Fire destroyed the mining camp in July 1910 and the following year Retallack and associates purchased the combined property. Operations continued on a reduced scale until 1922. The nine claims of the Whitewater group and 15 of the Whitewater Deep group were combined under the Whitewater Mines Ltd. in 1922, the final consolidation. Work was concentrated on the No. 11, 12 and 13 levels. The Metal Recovery Co. erected a small concentrator on the Kaslo River to treat tailings from the old Whitewater mill. A new mill was installed in 1928 which operated until July 1929, when operation by the company ceased. From 1932 to 1935 and briefly in 1937, the S.N. Ross Mining Syndicate operated the mine, mainly on the 1472 level. A 40-60 per cent partnership was agreed to between Whitewater Mines Ltd. and Kootenay Bell Gold Mines Ltd. under the name Retallack Mines Ltd. in 1943. Mill capacity was increased from 114 tonnes to 272 tonnes and put into operation in March 1944. Ore was mined from the 14 and 1472 levels in 1944, then in the vicinity of the No. 12 and 13 levels. Operations continued until 1952 during which considerable ore was recovered from the old Whitewater dumps. The Canada Trust Co. bought out Kootenay Bell Gold Mines Ltd. in 1953. The mill was sold in 1956 at which time the property was acquired by the Consolidated Mining and Smelting Co. of Canada. Over its mine life a total of 11 adits and 14 levels were mined over a distance of 550 metres downdip along the lode.

The Whitewater deposit consists of an upper zone characterized by veins and a lower zone characterized by structurally controlled replacement of limestone and lamprophyre. There are few surface outcrops at the Whitewater lode and most of the geology is known from exploration of the lode by adits. Mining occurred on 14 levels and several sublevels. The No. 14 adit was the principal working adit. Bulletin 22 gives a full description of the underground workings on Figure 5. The Whitewater lode is hosted by carbonaceous slates, slaty argillites, impure limestones and few quartzite beds of the Triassic Slocan Group. This strata is intruded by at least one porphyritic lamprophyre dike that is highly altered to carbonate and sericite and locally mariposite.

The upper zone occurs in a zone of shearing and fracturing in slates. The lamprophyre dike occurs as sheets and lenses within the lode and locally within the walls and intruded pre-mineralization. Above the No. 7 level the productive zone is up to 20 metres thick in sheared and brecciated hostrocks. Carbonaceous gouge and slickensides are well developed along vein walls. The productive zone extended down to the No. 9 level and one small stope on the 9.5 level. Ore consists of galena and sphalerite with minor tetrahedrite and trace pyrite and chalcopyrite, and occurs as streaks up to 20 centimetres wide, lenses and irregular pods up to 12 metres wide. Ore is hosted in a gangue of mostly siderite, as much as 1.5 metres, and some quartz. Ore in the uppermost levels is oxidized. Sphalerite contains cadmium in small amounts. The structure of the hangingwall was thought to be an important factor in localization of the ore as well as the flatter dip of the lode at this level.

The structure of the lower zone is complex. The Whitewater lode flattens abruptly below the No. 13 level from an average dip of 60 degrees to 20 degrees northward towards the lode. The footwall consists of slates and the hangingwall consists of limestone. Local silicification occurs around the replacement bodies. There are three ore types in the lower zone. The first type occurs as masses and lenses within the lode. The second ore type consists of massive replacement of limestone by sphalerite and siderite gangue. It constitutes the majority of lower zone ore and is referred to as the "spathic ore". Disseminated and locally massive galena comprises roughly one-fifth of orebodies. Pyrite and chalcopyrite are rare. Spathic ore occurs in overlapping lenses up to 10 metres thick, conformable to bedding with minor local silicification observed. On the No. 12 level the main orebody was 137 metres long by 2.4 metres wide, on average. The replacement bodies appear to be controlled by irregular-spaced fractures. The third ore type consists of sphalerite and galena in a gangue of magnetite, pyrrhotite, pyrite and other silicate minerals, replacing the lamprophyre dike. This ore, referred to as the "magnetic ore", occurs in relatively large bodies between the No. 12 and 14 levels. The maximum width is 12 metres and length 76 metres. Between No. 12 and 13 levels the limestone-slate contact is dragfolded, the dominant structural control localizing ore in the lower zone. These levels produced most of the ore between 1925 and 1935.

Northern Crown Mines Ltd. optioned the property in 1989 and conducted sampling.

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