Contact Group occurrence, Cassiar, Liard Mining Division, British Columbia, Canadai

Regional Level Types
Contact Group occurrence	Occurrence
Cassiar	- not defined -
Liard Mining Division	Division
British Columbia	Province
Canada	Country

The Contact Group occurrence is located 3 kilometres west of the Cassiar asbestos mine (104P 005), about 100 kilometres north of the community of Dease Lake, British Columbia.
The following quote is from B.C. Government site “Minfile”- Minfile No. 104P 004, current to 2014:
“A north trending, moderately east-dipping unit of Upper Proterozoic Ingenika Group (Stelkuz Formation) marble and hornfels lies between Late Cretaceous Contact quartz monzonite and Cassiar stock quartz feldspar porphyry and quartz monzonite. Two 070 to 080 degree striking fissure veins, up to 1.2 metres in width, crosscut the marbles. Manganiferous magnetite, galena, sphalerite and pyrite are the dominant minerals present. Molybdenite, pyrrhotite, arsenopyrite, chalcopyrite, tetrahedrite, albandite, bismuthinite, dyscrasite, native silver and bismuth occur as accessory minerals. Gangue consists of calcite, quartz and rhodonite.
Quartz veins also occur in Contact stock intrusive rocks. They strike southeast and dip to the northeast at low angles and contain pyrite, molybdenite, bismuthinite, scheelite and cosalite. A small pyrrhotite lens with minor chalcopyrite occurs in garnet-scapolite skarn in marble, about 30 metres from the Cassiar stock. Late aplite dikes cut the intrusive rocks.
The mine produced 10,451 grams of silver, 25 kilograms of copper, and 1947 kilograms of lead from 25 tonnes of ore in 1956 (Mineral Policy Branch).”
Comments by Giles Peatfield regarding some of the minerals reported:
Actinolite: McDougall (1953) described actinolite in veinlets cutting hornfels.
Alabandite: Thompson (1954) confirmed alabandite by X-ray analysis.
Andradite: This was reported by McDougall (1953) as probable – he also mentioned that it had an elevated Mn content. It was also reported by Gabrielse (1963), as part of a “garnet-scapolite” skarn in the southern part of the mineralized system. See comments below for “garnet”.
Anorthite: McDougall (1953) reported a feldspar as “labradorite - An60” from hornblende-basalt dykes.
Antimony: Wilson (1953) noted that native antimony was confirmed by X-ray analysis by Dr. R. M. Thompson at UBC.
Apatite: This was reported by McDougall (1953) in aplite bodies cutting limestone.
Augite: This was reported by McDougall (1953), from hornblende-basalt dykes in “marmorized limestone”.
Azurite: McDougall (1953) found traces of azurite in a coarsely crystalline calcite vein.
Bismite: This secondary Bi mineral was reported by Gabrielse (1963), and as “possible” by Kohse (1952).
Bismuthinite: This was confirmed by X-ray analysis (Kohse, 1952), presumably by Dr. R. M. Thompson.
Bournonite?: This is a tentative identification for Kohse’s (1952) “Unknown III”, occurring as small inclusions in galena – with a maximum size of 0.1 mm, and which he was unable to identify on the basis of etch tests. Kohse noted that Dr. H. V. Warren suggested that it might be a lead-antimonide. Greenwood (1954), working on material from the Wilms property (Marble Creek claims – Minfile No. 104P 006), a few kilometres to the south and with similar mineralogy, noted that his “Unknown II”, occurring as “worms” in galena, had all the same properties as Kohse’s “Unknown III”. Greenwood suggested that the mineral was probably bournonite; unfortunately, his X-ray pattern was “inconclusive”. His spectrographic analysis found lead and copper, but no antimony, which he could not explain. He also found no bismuth in the spectrum, which he believed excluded aikinite. More work would seem to be needed, were it possible to obtain material to study.
Cosalite: This was suspected by Dr. R. M. Thompson (see Kohse, 1952), reported by Gabrielse (1963), and confirmed based on microscopy and etch tests by Parry (1964). I would regard it as valid for the locality.
Diopside: Kohse (1952) reported diopside as a common gangue mineral in skarns around the Contact Group; McDougall (1953) reported diopside in hornfels and skarn.
Dyscrasite: This was confirmed by X-ray analysis by Dr. R. M. Thompson – see Wilson (1953).
“Garnet”: There is very little information available regarding garnets here. Kohse (1952) reported grossularite but did not give any specific data regarding identification. McDougall (1953) mentions grossularite, andradite and spessartine, but with no supporting data. He made the point that several of his “garnets” had elevated Mn contents.
Hematite: This was reported only by McDougall (1953), as a constituent of a skarn “vein”.
Hornblende: McDougall (1953) reported hornblende from a hornblende-basalt dyke and from aplite.
“Hydrocarbon”: McDougall (1953) described small amounts of an unspecified hydrocarbon in “porous and permeable wad” or manganese oxide (see “wad” below). He could not put forward any specific reason for its presence.
Magnetite: McDougall (1953), describing magnetite in the Contact vein, reported that “The mineral is strongly manganiferous, containing between 10 and 15 percent manganese.” Parry (1964) suggested that the mineral might be jacobsite (or mangoan magnetite?), but said that an X-ray analysis would be necessary to confirm jacobsite. I can find no evidence that such a determination has ever been done.
Molybdite: This was reported only by Gabrielse (1963), and should be regarded as tentative.
Pyrrhotite: McDougall (1953) made the point that some of the pyrrhotite, occurring as small rods in lead, zinc and manganese sulfides, was non-magnetic. He was not able to account for this property, but devoted several paragraphs to describing pyrrhotite in the main Contact vein.
Sericite: Parry (1964) reported sericite, and McDougall (1953) reported “white mica”, some of which was most likely sericite.
Smithsonite? McDougall (1953) described, as an alteration product, “. . . minute amounts of zinc carbonate.” By this he probably meant smithsonite.
Titanite: McDougall (1953) reported “sphene” in hornfels.
“Wad”: Several workers have reported “wad”; Thompson (1954) referred to it as “Mn oxide”. It is a common material in the deposit, presumably derived from manganese minerals such as alabandite and Mn-bearing magnetite.
Willemite?: McDougall (1953) reported a yellow alteration mineral on sphalerite which, based on its distinctive bright green fluorescence, he suggested was willemite.

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Link to British Columbia Minfile:	104P 004

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References