Quartz Silver (native)

Specimen Summary

Torbit Silver Mine. Alice Arm, British Columbia

Quartz is the second most abundant mineral on Earth, present in many different types of rocks. Although usually clear or milky white in colour, quartz is found in a variety of colours due to impurities in the crystal structure. Pure quartz consists of silicon and oxygen only, but atoms of other elements often make their way into the quartz crystal structure, colouring the crystals. Some varieties of quartz, like purple amethyst and yellow citrine, are considered to be semi-precious gemstones and have been used since ancient times to make jewellery and decorative objects. Well-formed (euhedral) crystals of quartz have a hexagonal cross section and are highly collectible.

Silver is an important precious metal. It is still highly valued today and has many important uses, as well as being used for jewellery. Silver has the highest electrical and thermal conductivity and reflectivity of all metals and is widely used in electronics and industrial chemistry. It is also used to make mirrors, photographic and x-ray film and collectible coins. Silver has natural antiseptic properties, therefore, has many different medical applications. Silver can occur in its elemental form as metallic silver, or in compounds and minerals with other elements like gold and lead. Silver has a distinct silver-grey colour and is soft and malleable, meaning it can be easily worked and shaped.

This sample comes from the Torbrit mine about 25 km north of Alice Arm in northern BC. The Torbrit mine was open from 1928 to 1959. In that time it produced 1,251,339 tonnes of ore containing 463.47 grams per tonne silver, 0.00538 grams per tonne gold, 0.389 per cent lead and 0.0441 per cent zinc. Most of this ore was mined in the last 10 years of the mine’s life.

The Torbrit orebody is relatively thin and flat. It follows a horizon of volcanically-derived sediments about 60 m thick for over 300 m in length. Sphalerite, galena and pyrite are the most abundant sulphide ore minerals in the Torbrit deposit. Silver was the main commodity produced by the mine, with lesser amounts of gold. The main gangue (waste) minerals are quartz, seen here, and barite.

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:

Association for Mineral Exploration (AME)

Sub Collection:

-

Collection ID:

AME-554

Virtual Museum ID:

19-AME554

Accessibility:

Date Added to VM:

2018-02-08

Location Information

Sample Origin:

Alice Arm, B.C.

Specific Site:

Torbrit Silver Mine

UTM Easting:

468093

UTM Northing:

6171355

Datum:

09 (NAD 83)

Coordinate Accuracy:

Approximate

Specimen Details

VM Category:

Mineral

Primary Features:

Quartz Silver (native)

Primary Mineral Formula:

SiO2, Ag

Primary Category:

oxide native element

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:

Hazelton Groups

Geological Period:

Lower to Upper Jurassic

Stratigraphic Age:

Geological Belt:

Stikine

Geological Terrane:

Intermontane

Minfile ID:

103P 191

Minfile Link:

https://minfile.gov.bc.ca/Summary.aspx?minfilno=103P++191

Site Details:

The Torbrit mine occurs on the east bank of the Kitsault River, 23.5 kilometres north of the town of Alice Arm. Between 1949 and 1959, Torbrit Silver Mines Ltd. produced 1,249,942 tonnes of ore containing silver, lead, zinc and gold.

The area is underlain by a sequence of volcanics and sediments of the Upper Triassic Stuhini Group and the Lower-Upper Jurassic Hazelton Group. The sequence is folded into the doubly plunging, north-northwest trending Kitsault River syncline. This sequence has been regionally metamorphosed to greenschist facies.

The Torbrit orebody is comprised of a stratiform volcanogenic silver-zinc-barite exhalative horizon developed in a section of Hazelton Group andesitic pyroclastics on the east limb of the Kitsault River syncline. This horizon is enclosed in an overlying plagioclase porphyritic andesitic lapilli-ash tuff and an underlying andesitic crystal vitric (shard) tuff that have been variably propylitized, silicified and carbonatized at least 30 metres outward from the horizon.

The exhalite horizon strikes approximately 050 degrees for at least 300 metres and dips 45 degrees northwest. The deposit is up to 60 metres thick. Within the east end of this horizon lies a pod-shaped ore shoot up to 24 metres thick that plunges 30 degrees for at least 490 metres towards 295 degrees.

Faulting occurs along the footwall of the deposit with dip slip movement. The deposit is also cut by a later set of faults, with right-hand displacement of up to 15 metres, that strikes northwards between 030 and 135 degrees and dips between 65 and 80 degrees. Later horizontal faults displace the deposit up to 43 metres. It is cut by a series of lamprophyre dikes from a few centimetres to 3 metres wide, striking north-northeast and dipping steeply northwest.

Mineralization consists of pyrite, sphalerite and galena with minor chalcopyrite and traces of pyrargyrite, argentite and tetrahedrite interlaminated with quartz, calcite, barite, hematite, jasper, siderite, magnetite and chlorite. This well layered exhalite horizon exhibits local brecciation.

Between 1928 and 1959, 1,251,339 tonnes grading 463.47 grams per tonne silver, 0.00538 gram per tonne gold, 0.389 per cent lead and 0.0441 per cent zinc were produced from the Torbrit mine.

Combined (proven, probable, possible) reserves are 786,285 tonnes grading 311.9 grams per tonne silver, 0.42 per cent lead and 0.50 per cent zinc (Dolly Varden Mining Ltd. Annual Report 1971). Refer to Dolly Varden (103P 188) for 2015 resource estimate.

A fluid inclusion study coupled with geological and geochemical data suggests that the silver-rich deposits (Dolly Varden, 103P 188; Torbrit; North Star, 103P 189; Sault, 103P 233) in the Kitsault River area be related to each other and that they may be silver-rich analogues to Eskay Creek (104B 008). The Kitsault River deposits all formed near or at surface or at shallow depth in the waning stages of Hazelton arc volcanism. Their mineralization varies from multiepisodic and irregularly laminated to bedded. Colloform, crustiform, and comb textures clearly indicate high level deposition of quartz that formed under low temperatures in low saline environments such as a hot spring setting.

In 1990, Dolly Varden Minerals Inc. conducted a surface diamond drilling program on portions of the North Star (103P 189) and Dolly Varden (103P 188) deposits, and also to test the V zone and the northwestern extension of the Torbrit mine mineralization. One hole was drilled on the Anglo claim (Lot 934) to a depth of 290 metres. Refer to Dolly Varden for a comprehensive work history of the area.

In 2010, Dolly Silver Corporation conducted an exploration program on the Dolly Silver property which consisted predominantly of a detailed stream sediment sampling survey with associated geological mapping, prospecting, rock and soil sampling. A total of 81 rock samples, 19 soil samples and 150 stream sediment samples were collected. A concurrent helicopter-borne time domain electromagnetic (VTEM), magnetic and radiometric survey over both the Dolly Silver and Dolly Varden properties was also completed. Flight line spacing was 200 metres over the Dolly Silver property and 100 metres over the Dolly Varden property with a total of 941.7 line kilometres of data collected.

In 2016, Dolly Varden Silver Corporation carried out surface mapping and sampling, and completed 2311 metres of diamond drilling in 13 holes. Diamond drilling was carried out on the Torbrit deposit and in the Ace-Galena area (103P 208). Drilling at Torbrit intersected multiple mineralized zones including 2.0 metres of 2488.5 grams per tonne silver within a broader intersection of 19.4 metres grading 485 grams per tonne silver (Information Circular 2017-1, page 167).

In 2017, Dolly Varden Silver Corporation announced plans for 12,000 metres of diamond drilling at the Dolly Varden silver project. The project consists of the Torbrit, Dolly Varden (103P 188), Wolf (103P 198), and North Star (103P 189) deposits. Drilling between the Torbrit and Wolf deposits resulted in a new discovery (Central zone), with results that included 16.10 metres (13.19 metres true thickness) grading 269.0 grams per tonne silver, 0.30 per cent lead, and 0.21 per cent zinc. Follow-up drilling confirmed this discovery, returning results of 7.15 metres (6.72 metres true thickness) grading 1180.7 grams per tonne silver, 1.83 per cent lead and 0.26 per cent zinc. Drilling also discovered an eastern fault offset of the Torbrit deposit (Torbrit East, 103P 190), with assays including 13.00 metres (9.96 metres true thickness) grading 244.8 grams per tonne silver, 0.14 per cent lead and 0.09 per cent zinc. Within this interval was 5.00 metres (3.83 metres true thickness) grading 481.9 grams per tonne silver, 0.21 per cent lead and 0.12 per cent zinc (Information Circular 2018-1, page 137).

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