Beaverbank Slate Quarry
It is a lake today but it used to be a slate quarry that provided stone for Halifax roads in the 1800s.
The quarry was on the Beaverbank properties of Thomas Dean and C. Hopkins, about 200 feet west of the Dominion Atlantic Railway and Beaver Bank Road, according to a 1927 government report. Today, the former operation is on what is called Quarry Road.
The quarry’s proximity to the railway and road network would have been a significant advantage for it since shipping would be easy and inexpensive. Being so close to a large market like Halifax would also have been very helpful.
The quarry’s main opening (excavation) was about 700 feet by 40 feet. At the time of the report, the pit was filled with water so it could not be inspected, but it was said to be over 30 feet deep. There were also several other shallow openings, none of them deeper than ten feet.
Several thousand tons of slate were extracted from the quarry, but the site had not been worked since around the late 1880s, according to the report.
The slate was mostly used for paving flags (slabs) in Halifax. At the time of the 1927 report, slate from the quarry was still in use on Water Street, for example. Square slabs up to 7x6 feet and up to 4-5 inches thick showed “no deterioration after 40 or 50 years of hard wear,” according to the report.
The report suggested the quarry could be reopened to provide slate for roofs, construction material and slabs for switchboards. This was a reference to the fact that slate was replacing marble in the early 1900s as the base for electrical switchboards because slate does not conduct electricity (it is a good insulator) and it is fireproof. Although marble was actually a better insulator, slate had advantages over marble due to its superior toughness, ease of workability and lower cost. In that era, switchboards were similar in function to today's breaker panels.
Electrical slate needed to be strong and workable (i.e. it needed to be drilled and sawed without scaling). It also had to be uniform in composition and not contain magnetite and metallic veining which, if present, could conduct electricity. The producers of switchboards often had appliances to test slate for conductivity. For example, an apparatus that consisted of a transformer, a milliameter (an instrument for measuring electric current in milliamperes) and wires with brush-like terminals was often used. A wire was applied to one side of the slate slab while a second wire was brushed over the surface. The milliameter was used to identify any current that was being carried in the stone.
Just as slate replaced marble in switchboards, slate was later replaced by the steel casings we use for breaker panels today.
Nova Scotia’s early slate quarries often used small charges of black powder to free the rock but this created waste by reducing some of the rock to rubble. Channelling machines became the standard way to extract large blocks by using the rock’s planes of weakness, such as its natural grain. This produced much less waste. The blocks could then be split into slabs, usually about two feet thick, with tools like wedges, again taking advantage of the rock’s planes of weakness. These slabs were taken to a saw machine and splitting mill to produce slabs of specific size and thickness, based on customer specifications.
