DD Core displaying pyrrhotite and chalcopyrite

Virtual Museum ID: 19-RM02

Specimen Summary


Pyrrhotite is an iron sulphide mineral that is bronze to dark black in colour. Due to much more cost-efficient sources of iron such as iron stone, it is not mined unless it includes some of a more valuable commodity such as gold or silver. One very interesting property of pyrrhotite is that it is variably magnetic. This property is based on having iron in the overall mixture of elements in the mineral. Varieties of pyrrhotite with less iron are more magnetic. Pyrrhotite is often found as a constituent in mafic rocks of igneous composition, and in that case, it is associated with a more valuable mineral called pentlandite.

Chalcopyrite is the most common ore mineral for copper and is a sulphide of iron and copper. Chalco comes from the Greek word chalko, meaning copper. Chalcopyrite is commonly found in sulphide deposits in most ore-forming environments. Chalcopyrite is an important copper ore mineral found in many different types of copper deposit. A characteristic deep brass yellow colour and iridescent green-to-purple weathering surfaces distinguish chalcopyrite from gold and sulphides such as pyrite. It is sometimes mistaken for Gold because of its bright yellow colour; however, it is harder, more common, and chalcopyrite commonly occurs with other copper sulphide minerals such as bornite and weathers to malachite and azurite.

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:

Rossland Museum & Discovery Centre (RM)

Sub Collection:

-

Collection ID:

RM_02

Virtual Museum ID:

19-RM02

Accessibility:

Date Added to VM:

2019-06-08

Location Information

Sample Origin:

Rossland, B.C.

Specific Site:

Le Roi Mine (Au-Cu)

UTM Easting:

440929

UTM Northing:

5436510

Datum:

11 (NAD 83)

Coordinate Accuracy:

Specimen Details

VM Category:

Mineral

Primary Features:

DD Core displaying pyrrhotite and chalcopyrite

Primary Mineral Formula:

Primary Category:

Secondary Features:

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:

Elise Formation (Rossland Group)

Geological Period:

Lower Jurassic

Stratigraphic Age:

178.9 to 185.6 Million Years

Geological Belt:

Omineca

Geological Terrane:

Quesnel, Plutonic Rocks

Minfile ID:

082FSW093

Site Details:

The Le Roi, Centre Star, and War Eagle claims, located at the northwestern edge of the city of Rossland, formed the nucleus of a property that was subsequently expanded by the Consolidated Mining and Smelting Company of Canada Limited (Cominco) to include some 30 claims and fractions. The three claims were located in 1890 by Messrs. Bourjouis and Morris, the Le Roi claim being recorded in the name of E.S. Topping.

The Le Roi claim was reportedly developed by a Spokane company, the Le Roi Mining & Smelting Co., from 1891. The Le Roi Mining Company, Limited, acquired the Le Roi and Black Bear claims in 1898 and the mine operated continuously until it closed in September 1910. The property was acquired by Cominco in 1911.

Cominco purchased the adjoining Josie property in 1923. By 1928 when the company closed the mine the original workings had all been connected underground to form one large mine with a total of about 97 kilometres of underground workings; mining operations were carried on to a depth of about 503 metres.

Groups of lessees, sometimes over 30 in number, extracted remnants of ore from the old surface and underground workings from 1932 until the company closed down the operation in June 1942; Cominco carried out a program of geological mapping during 1940-1941.

In May 1967 Hunstone Ventures Ltd. obtained an option from Cominco on 72 Crown-granted claims, including the mine workings of the Le Roi, Centre Star, War Eagle, Iron Mask, Josie, Kootenay Columbia, Nickel Plate, and Crown Point claims. By an agreement of August 1, 1967, Hunstone assigned the agreement to Falaise Lake Mines Ltd. During 1967-1968 Falaise carried out 3194 metres of surface diamond drilling, in 41 holes in the hanging wall of the Le Roi, Centre Star, and War Eagle veins, and magnetometer and electromagnetic surveys over other parts of the property. Based on this drilling, together with the work by Cominco in 1940, the indicated ore reserves in pillars and stope remnants in the upper part of the Le Roi, Iron Mask, and War Eagle workings were estimated at 278,800 tonnes averaging 79 grams per tonne gold, 20.9 grams per tonne silver, and 0.65 per cent copper. In May 1969 an adit was begun at the north edge of the Golden-Born Crown-grant (Lot 1234) and directed towards the 800 level crosscut of the Le Roi workings. The adit, driven for 1310 metres, was completed in October 1970. Underground diamond drilling was carried on into 1971. The option was subsequently dropped.

The southern part of the Rossland area is underlain primarily by volcanic rock of the Lower Jurassic Elise Formation (Rossland Group). These rest unconformably on metasedimentary rocks of the Pennsylvanian and possibly Permian Mount Roberts Formation and are in apparent fault contact with rocks of Unit Cs of Carboniferous age (both Upper Paleozoic units may be correlative with the Milford Group). Locally, the Elise Formation is overlain by coarse conglomerates of the Upper Cretaceous Sophie Mountain Formation.

Four prominent igneous suites intrude these rocks. The Rossland monzonite, recently dated at 190 million years (Early Jurassic), is and east trending intrusive complex centred near the Rossland gold camp. It is cut by the Middle to Late Jurassic Trail pluton (Nelson Intrusions) and by the alkaline Middle Eocene Coryell Intrusions. The Middle Eocene Sheppard Intrusions occur as stocks in the southeastern part of the area and in north-trending felsic dykes; they are also cut by the Coryell Intrusions. Also important is an augite porphyry intrusion known as the Rossland sill that hosts a number of the principal orebodies of the camp. The sill, exposed south of the monzonite and on the east slopes of Red Mountain, intrudes the upper part of the Elise Formation and is considered to be part of that formation.

The Rossland mining camp is the second largest gold-producing camp in British Columbia, with recovery of more than 84,000 kilograms of gold and 105,000 kilograms of silver between 1894 and 1941. These deposits are classified as three main types referred to as the North belt, the Main veins and South belt. The Rossland gold-copper veins are dominantly pyrrhotite with chalcopyrite in a gangue of altered rock with minor lenses of quartz and calcite.

In the North belt, a zone of discontinuous veins extends eastward from the northern ridge of Red Mountain to Monte Cristo Mountain. The veins strikie easterly and dip north at 60 to 70 degrees. The largest, on the St. Elmo claims (082FSW134), is in the Rossland sill and is 1 to 2 metres thick.

The Main veins form a continuous well-defined fracture system that trends 070 degrees from the southern slope of Red Mountain northeast to the eastern slopes of Columbia Kootenay Mountain, a distance of over 1 kilometre. More than 98 per cent of the ore shipped from the Rossland camp was produced from these veins, of which more than 80 per cent were from deposits in a central core zone between two large north-trending lamprophyre dykes. These important deposits include the Le Roi, Centre Star (082FSW094), Nickel Plate (082FSW095), War Eagle (082FSW097) and Josie (082FSW147) orebodies. The Main vein system consists of a series of veins, commonly en echelon, that dip steeply north. They are mostly within the Rossland sill or the Rossland monzonite. They crosscut lithologies and early structures, but appear to be cut by the late north-trending faults and associated dykes.

The principal veins of the South belt trend 110 degrees and dip steeply north or south. They are within siltstone lapilli tuff and augite porphyry of the Elise Formation, several hundred metres south of the Rossland monzonite. In addition to the typical copper-gold mineralization of the main veins and North belt, some veins in the south belt also contain sphalerite, galena, arsenopyrite and boulangerite.

The Le Roi deposit, part of the Main vein system, consisted of a series of ore shoots with narrow width or strike length with the greatest dimension on the dip. The ore shoots are strung out along a main fissure, which in general is nonpersistent, and end abruptly against dykes or cross structures. The Le Roi vein system strikes 070 degrees and dips 70 degrees north. The deposit was mined to about 600 metres elevation and explored vertically to a dimension greater than the strike length.

The vein system is hosted by the Rossland monzonite which is comprised of a biotite-hornblende-augite monzonite stock that intrudes augite porphyry of the Rossland sill. The porphyry occurs more than 450 metres below the footwall of the sill and is therfore older than the the monzonite intrusion. The augite porphyry in the mine area is thought to have been a stock or dyke-like feeder for the sill exposed on the surface. The monzonite is fine to medium-grained, grey to green in color and hosts magnetite, apatite, some sphene with chlorite, epidote, pyrite, and pyrrhotite. The Le Roi vein was formed by mineralization replacing wallrock along well defined fractures and by filling fractures and faults with pyrrhotite and chalcopyrite. The gangue consists of altered host rock with lenses of quartz and calcite. Actinolite forms rosettes of silky green needles between chalcopyrite and pyrrhotite. Minor pyrite occurs as well formed crystals in the pyrrhotite and as disseminations in the host rock. Garnet crystals are associated with the pyrrhotite and chalcopyrite which occur in fractures with quartz.

Native silver has been reported in pyrrhotite rich ore from the Le Roi central zone. It occurs as blebs along the grain contacts of pyrrhotite and at the contacts of pyrrhotite with magnetite and gangue. Small grains of a silver bearing mineral, probably stromeyerite, with heavy surface stain are associated with the silver.

Between 1898 to 1917, 1,791,680 tonnes of ore was mined from the Le Roi deposit from which was recovered: 24,091,170 grams gold, 37,563,105 grams silver, and 21,330,618 kilograms copper. Production from the deposit is reported to have commenced in 1893.

After 1917, between 1918 and 1942, production from the main mines (Centre Star, Josie, Le Roi, War Eagle, White Bear) was combined and recorded as the Rossland Properties.

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