Canadian Rockhound: The Pine Point Mine

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Geology of the Red Lake Mine, Ontario, Canada: the Richest Grade Gold Mine in the World
By Fuzail Siddiqui

Outstanding Giant Quartz and Sphalerite from Mont Saint-Hilaire, Québec
By Daniel Comtois

The Pine Point Mine
By Robert Carr, Mike Beauregard, and Peter Hager

Amber: The Dominican Republic's Gem which Inspired Jurassic Park
By Habeeb Salloum

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The Pine Point Mine

By Robert Carr, Mike Beauregard, and Peter Hager,
Yellowknife, Northwest Territories

Pine Point, NWT
(60°50' N, 114°28' W)

Up here, before there ever were mines, it was all moose pasture. The now-abandoned Pine Point mining district of the Northwest Territories is quickly turning back into prime moose pasture. This stretch of rockhounding real estate is about 90 km east of the town of Hay River and 10 km south of Great Slave Lake.

The mining district lies within the Presqu'ile dolomites of Middle Devonian age. Its lead-zinc deposits are known as Mississippi Valley Type or MVT. Perhaps 90 deposits, in all, have been found by geophysical surveys and diamond drilling. About four dozen of the deposits have been mined. Each paleokarst deposit is a solution-impregnated collapse zone within the confines of an ancient, vast cave system.

In 1898, samples of galena were reportedly shown by natives to prospectors bound for the Klondike gold fields. By 1930, drilling and shaft sinking by Northern Lead Zinc, Limited was started on lead-rich sinkholes. The Great Depression halted the work, but their reports indicated there could be 500,000 tons or more of reserves. A company called Pine Point Mines was established in 1951. A much larger company, the Consolidated Mining and Smelting Company, became involved. Now called Cominco Ltd, this major mining company began construction of a large mill (Figure 1) and 50+ homes in the early 1960s. The Pine Point townsite soon had all the amenities of a modern community. In 1981, the population was 1861 men, women and children. Infrastructure to support the 10,000 tons-per-day mining operation included Canadian National Railway's Great Slave Lake railway line driven from Manning Alberta up into the NWT, the Taltson River hydroelectric dam and an all-weather road. Concentrate was loaded onto railcars at the Pine Point mill. Long trains rolled down to Trail in southern British Columbia where the concentrate was processed. More than $2 billion worth of zinc and lead (at today's prices) was recovered by Cominco Ltd during the mine's 25 year lifespan.

Pine Point Mine
A

B
Figure 1: The Pine Point mine during operation. (A) Photo of the mill. (B) Photo of the mine pit.

Today, there is not one sign nor marker posted along the highway that passes by this venerable mining district. Pine Point simply no longer exists, not even as a ghost town! Depressed base metal prices coupled with high recovery costs forced Cominco to shut down operations in 1988. All buildings and most structures have since been removed. Many buildings and trailers remain in service after being transported to other towns. Reclamation of the minesite included the complete removal of the mill and re-establishment of drainage. Many of the waste piles were covered by dirt. Many of these man-made hills have now re-vegetated. Access roads into all pits were bulldozed shut and many pits are now small lakes brimming with water. Even the railway spur between Hay River and Pine Point was removed. Only a diesel power plant, a small cemetery, several communication towers and some paved streets are all that remains to remind us of Pine Point's history. Rockhounds (and moose hunters), though, are more interested in the 60 km long by 20 km wide system of haulage roads, pits and waste-rock dumps.

The collectable minerals of Pine Point include:

Barite (rare)
Limonite
Bitumen (or kerogen)
Marcasite
Calcite
Pyrite
Chalcopyrite (rare)
Selenite (rare)
Dolomite
Siderite (rare)
Galena
Sulphur (native form)
Sphalerite
Diverse fossils, mainly corals, of Devonian age

Galena:

Galena
Figure 2: Galena, thumbnail specimen. RC col.

Galena from Pine Point was presented in "Rocks and Minerals" (Jan/Feb issue, 1989). Galena from Pine Point is often found with a calcite druse or with dull faces. The cubic form is typical, but there can be some interesting modifications such as repeating twins or parallel growths up to several centimeters in length (Figure 2). There are also elongated cubes, some with hoppered edges. Most of the galena was put through the mill but some occasionally turns up in the waste piles.

Calcite:

There are many calcite crystals waiting to be found at Pine Point. Colour is usually milky white but there are amber-coloured specimens along with transparent to semi-transparent crystals (Figure 3). Some rhombs appear as almost perfect cubes. Twins are common as are parallel twins stacked one upon the other. Crystals are often perched on other calcite crystals or on crystalline dolomite. People have collected calcite at Pine Point for years. There is even the story of miners finding a walk-in pocket lined with calcite crystals, but it was destroyed in the next blast of that bench.

Calcite
Figure 3: An outstanding amber-coloured, semi-transparent crystal of calcite. Hand-held size. MB col.

In the summer of 2002, collector Mike Beauregard found a large milky white scalenohedral crystal (now in col. of Robert Carr). The crystal is abundantly overgrown with millimeter size tabular plates in parallel growth, along with much larger plates, terminating at the top with a perched large tabular twin (Figure 4).

Calcite
Figure 4: This exceptional calcite specimen consists of millimeter size tabular plates in parallel growth, along with much larger plates, terminating at the top with a perched large tabular twin. RC col.

Sphalerite:

Much of the sphalerite is of a black to dark brown colour. Sometimes these nodules or crystals are found as rosettes sitting on crystalline dolomite (Figure 5). Sphalerite can also form columns, with hollow centers lined with tiny sphalerite crystals or even "log" like columns growing through galena/sphalerite crystalline masses. One form of colloform ore has botryoidal 'tree-like' growth rings of sphalerite mixed with galena, calcite and sometimes sulfur.

Figure 5: Sphalerite rosettes sitting on crystalline dolomite and galena. RC col.

Dolomite:

Dolomite is literally everywhere at Pine Point and is typically crystalline with curved faces, forming aggregates of many small, offset crystals. Local collectors often refer to crystalline dolomite as 'saddle dolomite' (Figure 6). These can make for quite beautiful pieces when found in plate or dome-like assemblages. Colours are white or tan plus rare yellow, blue or pink tints. Often perched on these dolomites are calcite crystals of many shapes and sizes, giving each piece a nice solid matrix. Galena, sphalerite and/or sulphur crystals can also be found perched on dolomite or vice-versa (Figure 7). Combinations of all these minerals in crystal form are sometimes found.

Figure 6: Saddle dolomite "branch". MB col.

Dolomite on sphalerite
Figure 7: Dolomite on globular Sphalerite. MB col.

Selenite (Gypsum):

Gypsum is much rarer than some minerals, but it occurs as elongated bladed crystals, many as "fish tail" or "swallow tail" twins. These are clear or milky in colour.

Barite:

Some barite has been found, but nice crystals are rare. The crystal shown in Figure 8 was collected from a waste dump in 2002. It gives a specific gravity of 4.3.7 and measures 60 mm wide, 113 mm long, and 20 mm thick.

Barite
Figure 8: Barite, size: 60 x 113 x 20 mm. PH col.

Sulphur:

A surplus of native sulphur occurs in the carbonate rocks, particularly towards the west end of the Pine Point mining district. While individual crystals up to several centimetres in size sometimes form in vugs, specimens are fragile and usually do not survive collection.

Field Notes

In the summer of 2002, a few from Yellowknife made the long journey down to Pine Point. We persevered, despite mixed weather, throughout the summer. There are plenty of camping areas to choose from. There is the Calcite Crystal pile (stumble out of your tent and stub your toe on rhombic objects, large and small) or the Precambrian 'Hills of Till' gravel burrow pit (lapidary rocks, some subtle fossils and a burgeoning heap of "leav'er-ite's"). Then there are the open pits, complete with vertical walls where you can stand up on top along the edge and peruse crystal pockets with your pair of binoculars, but it's too dangerous to climb. And we can only wonder what lies hidden beneath the waters that are filling the pits. Folks seem to like the dumps of waste rock from which to collect. The larger the dump, the better. After handling sulphur, we smell like matchsticks. The bitumen (or kerogen) found at Pine Point is a neat petroleum product halfway between tar and coal. On hot days, it slowly oozes out of the rocks. We have yet to see it oozing but the evidence is compelling. Collecting from a pocket of calcites is always exciting as you can feel the crystal shapes, often under a coating of clay. Crystals are removed as carefully as possible but usually remain coated for the trip home, where they are then washed off. This is when you find out what damage was done in the initial digging. So will it be another trip to try, try again to collect undamaged or "undinged" specimens? Now we're off to clean and sort and squint and label. With our long winter season, we can spend up to eight months dreaming about next year's collecting at Pine Point.