Pyrite-chalcopyrite-arsenopyrite(?)-quartz vein

Virtual Museum ID: 19-D34-19

Specimen Summary


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.

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.

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.

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:

Smithers Exploration Group (SEG)

Sub Collection:

Snip Gold Mine

Collection ID:

D34-19

Virtual Museum ID:

19-D34-19

Accessibility:

Date Added to VM:

2019-02-21

Location Information

Sample Origin:

Near Craig & Iskut River, B.C.

Specific Site:

Snip Gold mine

UTM Easting:

370764

UTM Northing:

6282486

Datum:

09 (NAD 83)

Coordinate Accuracy:

Specimen Details

VM Category:

Mineral

Primary Features:

Pyrite-chalcopyrite-arsenopyrite(?)-quartz vein

Primary Mineral Formula:

FeS2 · CuFeS2 · FeAsS · SiO2

Primary Category:

sulphide oxide

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:

Stuhini Group

Geological Period:

Upper Triassic

Stratigraphic Age:

145 to 163.5 Million Years Ago

Geological Belt:

Intermontane

Geological Terrane:

Stikine

Minfile ID:

104B 250

Site Details:

The Snip mine area, near the junction of the Craig and Iskut rivers is underlain by a series of folded and faulted volcanics, volcaniclastic and clastic sedimentary rocks of Mesozoic age.

The Snip mine itself is underlain by a sequence of fine to coarse grained feldspathic to lithic greywackes with lesser intercalated siltstone, mudstone and conglomerate. This sequence is correlated with the Upper Triassic Stuhini Group. The Snip deposit is hosted within a 200-metre interval of biotite altered, feldspathic to lithic greywacke in this lower sedimentary sequence.

These layered rocks are intruded by intermediate to felsic stocks and plutons of Jurassic and younger age that are related to the Tertiary-Jurassic Coast Plutonic Complex. The area is extensively cut by regional thrust faults and more regional northeast and northwest striking normal block faults.

The Twin zone is a 0.5 to 15-metre wide sheared quartz- carbonate-sulphide vein that cuts through a massively bedded feldspathic greywacke-siltstone sequence. Bedding strikes from 045 to 100 degrees and dips 10 to 45 degrees northwest. A post-mineralization dike divides the vein into two parts for most of its length.

Massive sulphides occur in foliation-parallel veins of predominantly massive pyrite 5 centimetres to more than 1 metre thick. Massive pyrrhotite is present locally. Other significant sulphides include, in decreasing order of abundance, arsenopyrite, sphalerite, chalcopyrite and galena. Streaks of magnetite occur in some pyrite veins with 1 to 5 per cent disseminated pyrrhotite. Both black biotite and annite streaks are associated with the sulphides, but seldom exceed more than 10 per cent of the vein volume. Calcite is interstitial to sulphide grains in most veins and quartz eyes are common in pyrrhotite-rich ore. Both chalcopyrite and fine (less than a millimetre) visible gold are commonly spatially associated with the quartz.

Quartz mineralization consists of foliation-parallel quartz veins containing the same sulphide species as the massive sulphide veins, but sulphide content seldom exceeds 2 per cent. The relative abundance of pyrite is generally less than that in massive sulphide mineralization; other sulphides, notably pyrrhotite and chalcopyrite, are proportionally more abundant. Annite. and less abundantly, black biotite, commonly comprises 5 per cent of the quartz veins, but locally forms up to 50 per cent of the vein. Bladed quartz-annite intergrowth is common in veins with abundant annite. Blades are generally perpendicular to the vein walls.

Quartz veins are invariably strongly fractured and have been described as "crackle quartz". Fractures are usually filled with calcite and/or iron carbonate, giving the quartz veins a carbonate content of 1 to 4 per cent. Annite and sulphides may also occur as fracture filling. Visible gold is usually associated with or enclosed in sulphides and annite as fine, free gold, but may also occur as disseminations in unfractured quartz.

Progressive increase in sulphide content over distances of 1 to 2 metres commonly produces a gradation from quartz to sulphide vein mineralization, implying a genetic relationship between these two ore types.

The Twin zone mineralization consists of two zones occupying a 120-degree structure with dips varying from 30 to 90 degrees southwest. The dip length of the deposit is about 500 metres and has been traced over a strike length of 1000 metres. Minor/trace amounts of bismuth and lead tellurides, including tellurobismuthite, cosalite, hessite and volynskite have been noted in thin sections. Narrow parts of the mineralized zone often comprise dominantly one band of sulphide while thicker sections show repetitive banding of all ore types. The thicker sections also contain interbands of biotite-carbonate-potassium feldspar-altered feldspathic wacke. Later shearing has developed a strong to moderate foliation within this zone and is best defined in the biotite (chlorite)-rich bands. Vein boundaries are usually sharp with well-defined gold values plus lower grade values in the immediate footwall and hanging wall. Minor fault offsets were noted, and extensive right lateral tension gashes are common.

Gold mineralization occurs in 1 centimetre to 1 metre alternating bands of massive (streaky) calcite, heavily disseminated to massive pyrite, biotite-calcite as thin bands or streaks, or in quartz with sulphides in a crackle breccia or pyritic to non-pyritic fault gouge.

Work History

The Snip 1 and 2 claims, located by Cominco Ltd. in 1982, were staked over the company’s Red Bluff property and adjacent ground. A gold showing was discovered at about 670 metres elevation on Snip 1 claim on the lower northwest slope of Mount Johnny 1 km west of and on the opposite side of the ridge from the Red Bluff claims. In 1985, Cominco carried out a geochemical survey comprising 36 soil and 26 rock samples.

Delaware Resources Corp. optioned a 50 per cent interest in the property in 1986. Work that year included geochemical soil surveys, trenching, and 1494 metres of diamond drilling in 13 holes. The agreement was renegotiated in early 1987 giving Delaware the right to earn 100 per cent interest subject to Cominco backing in for a 60 per cent interest. In 1987, Cominco, as operator of the joint venture, completed about 14 000 metres of diamond drilling in 73 holes. Underground exploration was started in March 1988. Delaware Resources and Colossus Resource Equities merged into Prime Resources Corporation. Underground exploration was carried out on the 180, 300 and 340 metre levels. Between August 1988 and October 1989, 41,000 metres of underground diamond drilling and 4200 metres of underground work were completed and by mid-1990, 63,700 metres of surface and underground diamond drilling were completed. In 1990, Prime Resources Corp became Prime Resources Group Inc.

Reserves estimated by Cominco at January 1, 1995 were 625,000 tonnes grading 26.5 grams per tonne gold (Information Circular 1995-9, page 6).

Proven and probable ore reserves at January 1, 1996 were 347,782 tonnes grading 26.7 grams per tonne gold. In addition, there are possible reserves of 132,890 tonnes grading 23.6 grams per tonne gold (George Cross News Letter No.64 (March 29), 1996).

In 1997, Homesake Canada Inc continued to explore the Snip property with 12 BQ drillholes totalling 2788 metres on the Jim 1, Jim 2 and Mining Lease 37.

Proven and probable ore reserves at January 1, 1997 were 334,720 tonnes grading 24.7 grams per tonne gold. Geological resources were 17,235 tonnes grading 19 grams per tonne gold (George Cross News Letter No. 25 (February 5), 1997).

The Snip Mine is owned and operated by Prime Resources Group Inc. at January 1, 1998 were 210,470 tonnes grading 23.25 grams per tonne gold. Geological resources (mineralized material) were 23,590 tonnes grading 25.75 grams per tonne gold (Prime Resources Group Inc., Press Release, January 22, 1998).

In December 1998, International Skyline Gold and Homestake Canada, a wholly owned subsidiary of Homestake Mining, agreed to explore and possibly mine a portion of Skyline's claims neighbouring the Snip mine. See Bronson Slope for details (104B 077).

Mining was completed, and production suspended during the second quarter of 1999. Reclamation activities have started and will be completed by the end of 1999. Recovery of about 2500 kilograms of gold from the tailings pond may be considered.

From 1991 to 1999, the Snip Mine produced 32.093 million grams of gold, 12.183 million grams of silver and 249,276 kilograms of copper from about 1.2 million tonnes.

In 2016, Skeena Resources Limited) completed 7,180 metres of diamond drilling in 28 holes on the Snip past producing mine. Drill results identified or confirmed three significant high-grade zones all of which are outside of historic mine working areas. Highlight results included 33.07 grams per tonne gold over 2.4 metres for the Lamp Zone, 16.24 grams per tonne gold over 13.5 metres for the 200 Footwall Zone and 16.01 grams per tonne gold over 4.7 meters at the Twin West structural corridor (Exploration in British Columbia 2016, page 165).

In July 2017, Skeena Resources Limited acquired 100 per cent interest in the Snip past-producing gold mine from Barrick Gold Corporation. Highlight results included 341.00 gram per tonne gold over 1.50 metres, 67.68 grams per tonne gold over 2.03 metres and 10.76 grams per tonne gold over 4.30 metres including 14.80 grams per tonne gold over 1.49 metres and 9.47 grams per tonne gold over 1.50 metres corridor (Exploration in British Columbia 2017, page 27). Skeena reported that drilling verified historical data. For 2018, they plan to expand the known mineralized zones and to examine previously overlooked areas.

Additional Images