Arsenic pyrite gold
Virtual Museum ID: 19-StM07
Arsenic(As) is a very brittle element that can be tin-white, tarnishing to dark grey or black. Can be found in pure elemental crystal but is usually found in combination with sulfur and metals. Arsenic has many industrial uses some of which include: bronzing, pyrotechny, insecticides, and poisons, and as a doping agent in transistors to name a few.
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.
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, as seen in this sample. In its natural mineral form, gold is commonly alloyed with silver. Gold is distinguishable by its characteristic golden yellow colour and extreme heaviness.
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:Stewart Museum (StM)
Virtual Museum ID:19-StM07
Date Added to VM:2019-08-15
Sample Origin:NE of Mount Davidson, B.C.
Specific Site:Erickson Mine
Datum:09 (NAD 83)
Primary Features:Arsenic pyrite gold
Primary Mineral Formula:FeS2, Au, H3AsO4 or AsH3O4
Primary Category:native element sulphide
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:Sylvester Allochthon
Geological Period:Upper Paleozoic
Stratigraphic Age:541 to 251.902 million years ago,
Geological Terrane:Slide Mountain
Minfile ID:104P 029
The Erickson mine, located 12 kilometres southeast of the former mining town of Cassiar, began production on the Jennie vein in 1978.
Gold and silver-bearing white quartz veins occur in the Sylvester Allochthon, which is in this area of Upper Paleozoic age. The Sylvester Allochthon is a fault bounded imbricate assemblage of Devonian to Triassic regionally metamorphosed (greenschist facies) oceanic rocks thrust over autochthonous North American sediments. In this area, the assemblage consists of Slide Mountain Complex greenstones, pillow metabasalts, serpentinite, listwanite and argillites. West plunging veins occur on both limbs of a synclinal fold with an east trending axis.
Two types of gold-bearing structures occur. Cymoidal quartz-filled sheared fault structures dip north or south forming ore where they pass from competent to incompetent rock types. The Jennie, Maura, Alison and Caitlin veins belong to this type. The Devine, Bear, Goldie and Dease are tension fracture veins. The McDame is a late-stage vein consisting of layered dolomite, clear quartz, pyrite and calcite. The Kelly vein, just north of the Bear vein, is presently in the exploration phase. Veins are up to 5 metres thick with alteration envelopes commonly being 1 to 15 metres thick.
Mineralization in the Erickson veins consists of pyrite, tetrahedrite, chalcopyrite, sphalerite, arsenopyrite, covellite and gold. The gold is associated with chalcopyrite and tetrahedrite as well as occurring along in quartz-bearing fractures. Tetrahedrite occurs as blebs and fine disseminations with associated chalcopyrite. Malachite and azurite staining is common in the veins.
Listwanite, and less common carbon-bearing alteration envelopes, are well developed. Where quartz veins cut or lie directly underneath a listwanite zone, the gold values for that portion of the vein increase. Dussell (1986) proposed that "ore solution infiltrated and metasomatized bodies of partially serpentinized peridotite producing a listwanite. Gold precipitation was then triggered by a decrease in sulphur activity when the ore solution reacted with the listwanite parent".
To date, Erickson Gold Mining Corporation has produced 489,780 tonnes of ore grading 15.6 grams per tonne gold and 11.31 grams per tonne silver (includes the Vollaug (104P 019), Wildcat (104P 057) and Table Mountain (104P 070) (A. Boronowski, personal communication, 1988).
The potential mineral resource for the property is 199,562 tonnes grading 22.9 grams per tonne gold (George Cross News Letter No.243, 1991).
Total Energold Corp. suspended production at the Erickson mine in late October, 1988. See Table Mountain for subsequent production in the area.
Cusac Gold Mines Ltd. estimates mine tailings from the 1979 to 1988 period contains 700,880 tonnes averaging 1.25 grams per tonne gold which is 70 per cent recoverable (Exploration in British Columbia 1998, page 24 and George Cross News Letter No.203 (October 22), 1998).
In 1998, Cusac Gold Mines Ltd. carried out a program of overburden trenching and vein sampling to expose and evaluate an extension of the Bear vein. Originally discovered by Erickson during the course of driving the 21 Level drift, this Type 1 vein was partially mined out from the 21 and 14 Levels. Exploration drilling in 1997, designed to test for veining east of the Erickson Creek Fault Zone and east of the Main Mine Area, yielded several interesting intersections on a Bear Vein extension. Additional follow up holes began to define a near surface mineralized shoot. The decision was taken in late 1997 to halt drilling on the structure and to undertake a trenching and samp1ing program to determine the continuity of the structure and of gold grade within the structure. Initial samp1ing yielded gold grades sufficient to warrant the extraction of a bulk sample and is currently underway (August 30, 1998).
In 2007-08, Hawthorne Gold Corporation and Cusac Gold Mines Ltd. entered into a merger agreement whereby the two companies would continue to operate under the corporate entity of Hawthorne Gold Corporation. Hawthorne became the owner and operator of Cusac’s Table Mountain (104P 070) and Taurus (104P 012) properties and proceeded to form a private subsidiary company, Cassiar Gold Corporation, to retain assets acquired from Cusac. The entirety of this land package became known as the Cassiar Gold property. Table Mountain project areas contain the historic Erickson Gold Mines mine site (104P 029) located adjacent to the southern shores of McDame Lake, historic underground workings at the Main Mine area along Erickson Creek, historical portals used to mine and access the Vollaug vein (104P 019) on top of Table Mountain and east of the Main Mine, and the Cusac and Bain Portals approximately 8 kilometres south of the Main Mine. The Taurus project area is approximately 6 kilometres north of the Main Mine and contain the historic Taurus, Sable, and Plaza portals and underground workings. The intent of the 2008 exploration year was to reassess the overall scope of the Cassiar Gold property. The exploration program comprised field reconnaissance, soil sampling (606 samples), rock and chip sampling (365 samples), airborne magnetic and VLF-EM surveying (6567 kilometres), geophysics ground truthing, and diamond drilling (15 holes totalling 2536.5 metres on the East Bain vein, 104P 070).
In 2010, Cassiar Gold Corp., a wholly owned subsidiary of China Minerals Mining Corporation, completed a helicopter-borne time domain-EM, magnetic and radiometric survey covering 5090 line kilometres.