Dundas Quarry - Hidden Treasures!

Location - Lafarge Quarry

The Lafarge Quarry is located in Dundas Ontario, near Hamilton, on highway 5, 6km west of the junction between highway #5 and highway #6.

1.8 metres, (6 feet) of Guelph dolostone underlain by 13 metres (44 feet) of Eramosa Dolostone of the Lockport Formation.

Left: A small cluster of celestine crystals. Tim Elliott.

The quarry is one of Ontario's largest and has produced over 1 million tons of crushed stone for concrete aggregate, road stone, railway ballast, as well as agricultural limestone, stone for lining open-hearth furnaces, flux-stone for the steel industry and stone for the dead-burned dolomite refractory plant of Lafarge Canada. About half the quarry production was used in the metallurgical industry.

Dead burned dolomite was produced in a kiln fed with 18.5 tons of dolostone per hour and 3- 3.5% fine magnetite added. The kiln was fired with powdered coal. Product called klinker was discharged into a cooler and then on to a crusher. The screened product was then mixed with bunker B oil to control dust. This product was shipped to steel producers in Hamilton, Sault St. Marie and Sydney Nova Scotia.

Why the minerals are there
Sub economic concentrations of Mississippi Valley-type lead and zinc sulphides are found at numerous locations throughout southern Ontario. The mineralization is found in dolostones.

The process started when calcarious sediments accumulated on the sea bed. Sea water and then shallow to late burial fluids seeped through the sediments, gradually turning them into limestones. Later during continued burial of the limestones, Magnesium-rich fluids, probably derived from deeply circulating seawater, transformed the limestones (calcium carbonate) into dolomite (calcium magnesium carbonate). This process called "dolomitization" commonly causes a variety of cavities or pores to form. In addition, dolomitization also caused well-preserved fossils in the original limestone to be modified into more fuzzy, less distinct impressions in the newly formed dolostone.

Left: Tim Elliott with one of the calcite clusters found in a vein/fissure. Photo credit: Bill McIntyre.

Warm brines (<65 degrees Celsius) flowed through shales in the sedimentary sequence picking up zinc, lead and iron as chlorides together with hydrocarbons. These hydrocarbons provided the sulphur as hydrogen sulphide which then reacted with the metal chlorides and precipitated various sulphides such as sphalerite, pyrite, marcasite and galena. These minerals typically crystallized in holes in the dolostone, but in some cases also replaced the dolomite. The hydrocarbons were likely derived from the organic-rich dolomite of the Eramosa Member. The hydrocarbons are seen as a black coating in some of the cavities and on bedding surfaces of the dolostone.

Sulphide veins such as the one which provided rich mineral collecting in the mid 1960's were formed when brines interacted with surface waters, traveling along fractures in the rock. Late in the mineralization of the rocks the sulphates gypsum and celestine formed.

Mississippi Valley-type deposits
Deposits of lead and zinc sulphides, like we have in southern Ontario, can be linked to the regional scale geological processes that resulted from plate tectonics. Continental collisions cause large amounts of crustal fluid, which includes petroleum and metal-rich brines, to flow through sedimentary basins. Dating of the sulphide metals has suggested that most of the fluids migrated during the formation of the Appalachian and Oachita Mountains about 250 million years ago, after the last collision between Europe and North America.

Right: This specimen of galena cubes could possibly be the largest of it's kind ever found. W. & R. Mielke.

Winfried and Reiner Mielke
In the mid 1960's Reiner and his father Winfried Mielke worked hard on extracting specimens from a sulphide vein exposed at the time. They dug into the quarry floor and extracted spectacular specimens of dolostone coated with marcasite, and one centimetre galena cubes. A large specimen from this occurrence is now part of the Earth Sciences Museum collection at the University of Waterloo.

Tim Elliott
Tim started collecting at Dundas in January 2000 after getting a start on the "collecting bug" in the Bancroft area the previous summer. Since finding his first big celestine specimen there - he's hooked and spends every weekend collecting at the quarry (rain or shine, snow or sleet!)

Left: Sphalerite and small calcite crystals on dolostone. Tim Elliott.

This effort has paid off big-time with world-class specimens of calcite, fluorite, selenite and celestine being found on a regular basis. Spectacular specimens include 330 pound and 200 pound orange-yellow calcite clusters and yellow fluorite crystals 9 cm (3.5 inches) across. Celestine crystal clusters with crystals up to 15cm (6 inches) long have also been found. The massive calcite specimens are found in a vein/fissure 76cm (30") across and 6m, (20') high which was filled with glacial clay and sand. The clusters of calcite are found hanging on one wall of the fissure. The other wall of the fissure is covered with small dog-tooth calcites, 0.6cm to 0.9cm (1/4 to 3/8 inch) crystals. The first of the massive specimens was easily collected from the floor of the quarry where it rested after blasting. The second was more of a challenge to collect. The cluster was watched for seven months until a blast finally broke it free and it sat in the bottom of the fissure. A ladder was used to access the bottom of the fissure and the specimen was hooked out of the fissure to land on a snow pile. The specimen was loaded on a toboggan and dragged 1/4 mile across the quarry floor to the truck. The specimen looked like a big lump of frozen clay when collected with a slight hint of crystal structure. On the way home Tim stopped at the local car wash and power washed the clay and ice covering the beautiful calcite crystals. The collection is now creating lots of interest and was on display at the Royal Ontario Museum during February and March 2001. The collection will travel to other southern Ontario venues during the year.

The quarry gradually changes offering new opportunities for collecting. This year should be good for galena, sphalerite and marcasite as quarrying operations near a 4' wide sulphide vein similar to the one which the Mielkie's found in 1966.

Above right: An attractive selenite specimen. Tim Elliott









Above left: A large fluorite crystal. Tim Elliott.









Minerals found at the Dundas Quarry