Virtual Museum ID: 19-BCGS-ASHLU_87-2
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.
Chalcopyrite is an important copper ore mineral found in many different types of copper deposit. 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.
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:British Columbia Geological Survey (BCGS)
Virtual Museum ID:19-BCGS-ASHLU_87-2
Date Added to VM:2019-05-07
Sample Origin:45km NW of Squamish, B.C.
Specific Site:Ashlu Mine
Datum:10 (NAD 83)
Primary Features:Quartz Chalcopyrite
Primary Mineral Formula:SiO2 · CuFeS2
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:Coast Plutonic Complex
Geological Period:Jurassic to Cretaceous
Stratigraphic Age:201.3 - 66 Ma
Geological Belt:Coast Crystalline
Geological Terrane:Plutonic Rocks, Gambier
The portal of the former Ashlu mine is located at the confluence of Roaring Creek with Ashlu Creek, 45 kilometres northwest of Squamish, British Columbia.
The Ashlu mine area is underlain by extensive areas of quartz diorite, granodiorite and diorite bodies of the Jurassic Cloudburst pluton of the Jurassic to Cretaceous Coast Plutonic Complex. This pluton has intruded into and along the margins of Lower Cretaceous Gambier Group greenstone forming the eastern boundary of a major northwest trending pendant, east of the mine site. Regionally, these pendants are composed of andesite to rhyodacite flows and pyroclastics, greenstone, argillite and minor zones of conglomerate, limestone and schist. These pendant rocks may be metamorphosed up to amphibolite grade. A major north-west trending shear zone of Cretaceous age, the Ashlu Creek shear zone, in part defines the contact of the pluton and the pendant. Forming the western contact of the pendant is the Cretaceous Squamish pluton.
All mining was done along the plane of the vein, which dips 25 to 30 degrees west, striking approximately 010 degrees. At the lowest level the vein steepens to 35 degrees. The quartz vein is situated at the hangingwall of an elongated roof pendant consisting of biotite and amphibole hornfels which strikes 015 degrees and is up to 4.6 metres in width. The hangingwall, in contact with the quartz vein, and the footwall, in contact with the pendant, are composed of biotite granodiorite. Previous to 1994, many reports stated a complex, fine grained, dark, mafic-rich rock intimately associated with the quartz was a dike. Petrographic analysis indicates it is a phyllonite produced by cataclastic deformation along a fault (Assessment Report 4036). The quartz vein varies in width from 0.2 to 3 metres. Most of the underground workings follow this vein over a strike length of 90 metres and downdip for 85 metres.
The quartz vein consists of massive to cleaved white quartz with pods, streaks and disseminations of pyrite and pyrrhotite, especially near the vein walls. Minor amounts of chalcopyrite, scheelite, sphalerite, ankerite and siderite also occur in the vein. Gold values are closely associated with the sulphide minerals.
Petrographic studies show that the gold does occur in native form of very fine size (0.01 - 0.04 millimetre) but mainly it is associated with the tellurides: tellurobismuthite, calaverite, frohbergite, hessite and altaite. The tellurides occur as small grains in euhedral pyrite adjacent to the ore zone. In 1994, several additional distinct gold associations were made. Gold occurs as: 1) large inclusions (up to 0.1 millimetre) in pyrite, 2) blebs less than 10 microns in chalcopyrite, 3) native gold up to 40 microns along fractures in quartz, 4) native gold up to 50 microns along pyrite-quartz grain boundaries and 5) native gold up to 35 microns along fractures in pyrite (Assessment Report 24036).
The mine workings consist of a 120 metre drift adit driven southerly from Ashlu Creek, raises and stopes to the surface, 2 drifts some 30 and 60 metres below the adit level, a 30 degree winze connecting the drifts and crosscutting for a total of over 300 metres of underground development.
Proven and possible reserves are 89,350 tonnes grading 8.57 grams per tonne gold and 12.34 grams per tonne silver (MDAP Stage 1 Report, 1981).
The Ashlu quartz veins were discovered in 1923 by F. Pykett and associates, who originally called the claims the Golden King group. Over 30 metres of underground development were done in 1924. By 1930, the claims were known as the Gold Coin group, owned by the Pykett estate, C. Anderson and R.V. Carson. The Ashlu Gold Mining Syndicate set up a 23 tonne per day mill at the mine site which operated intermittently from May 1937 until October 1939 when the ore was depleted. In 1947, Giant Mines & Metals explored the area as the M2-5 mineral claims. Since 1975, about 1000 metres of diamond drilling have been completed on the deposit. Osprey Mining and Explorations Limited reportedly installed a 91 tonne per day mill in 1979, but except for 36 tonnes milled in 1984 no other production was recorded. Osprey Mining and Exploration leased the property from 1979 to 1985 and carried out an extensive development program. In 1985, Tenquille Resources Ltd. acquired the property and in 1987 retained Cooke Geological Consultants to carry out underground sampling. In 1988, Valentine Gold Corp. took an option on the property. As of 1994, the former Ashlu mine is staked as the Au claim and owned by L. Demczuk. The surrounding area was restaked as the Ashlu 1 to 5 claims by 421424 B.C. Ltd. and Homegold Resources Ltd was retained to prospect and geologically map the claims. During 2009 through 2012, Ashlu Mines completed a program of rock, soil and silt sampling on the area.