Ottawa Brook
The Newark Plaster Company operated a gypsum quarry at Ottawa Brook, Victoria County, from 1907-1927.
The quarry struggled in its early years due to sinkholes that prevented the company from obtaining a good-sized working face - none were taller than 15 feet, quite small by industry standards.
As a result, the Ottawa Brook quarry was actually several quarries that were considered one operation. By 1921 it had as many as five sites operating, including one underground which operated briefly around 1921. Nova Scotia has world-class gypsum deposits and with so much available near-surface, there generally isn’t any reason to incur the much higher costs of mining it underground. The brief underground operation at Ottawa Brook was unusual and likely done to address a site-specific challenge, i.e. there may have been a small reserve of gypsum that could only be accessed via a tunnel, but not enough to justify the costs of an ongoing underground operation.
The quarry’s early challenges with small working faces were eventually overcome. In later years, the working faces in the main quarry were approximately 40-50 feet in height, which allowed for greater operational efficiency. This was the result of moving operations to areas with fewer sinkholes.
Most of the gypsum was mined from one elongated pit about 600 metres north of the Canadian National Railway trestle at Ottawa Brook.
The gypsum was extracted using hand augers to drill holes in the rock. Black powder or “rack-a-rock” dynamite was inserted into the drill holes to blast the rock, freeing it from the face.
Stone was hauled by a narrow-gauge railway (3-foot gauge, 40-pound rails) to loadout facilities at McKinnons Harbour, 1.6 kilometres south of the quarry. A trail that roughly follows the old rail track leads to the site from the paved road.
A rock crusher at the pier crushed the rock down to 3-inch chunks and screened it to remove fines (fines are particles of rock resulting from the crushing process).
The two World Wars often caused significant challenges for Nova Scotia mines and quarries. In a number of cases, sites were even shut down due to the lack of labour and materials during wartime. While that was not the case in Ottawa Brook, the quarry extracted 925 tons of gypsum in 1916 but was unable to ship any of it because the company could not get any vessels to carry it.
A calcining plant was installed in 1920. (Calcining means to heat a mineral to the point of changing its mineral structure. It is part of the process of turning raw gypsum into plaster so it can be used in products like wallboard, mouldings and casts.)
At its peak from 1923-25, the quarry produced an average of 23,500 tons of gypsum per year and employed an average of 53 men.
A sketch of the quarry with its multiple working areas from the 1940s is below.
The area is known to have amazing gypsum deposits. The Little Narrows gypsum quarry is to the northwest and the historical Grass Cove quarry, just north of Iona, is to the east.
A classic karst terrain can be seen about two kilometres north of Ottawa Brook where there is a line of lakes called the Plaster Ponds. A karst terrain is characterized by numerous caves, sinkholes, fissures, and underground streams. The sinkholes are caused by groundwater naturally eroding rocks like gypsum that are water-soluble. The water erodes the rock, leaving an underground cavern. Eventually, the weight of the rock and earth above the cavern causes the sinkhole to form.
The Plaster Ponds are depressions left at surface when the rock and earth sank into the underground cavities. They filled with water, forming beautiful ponds.
Nova Scotia has traditionally been one of the world’s biggest producers of gypsum, supplying many plaster, and later wallboard, factories on the US east coast. Today, the walls of most Nova Scotian homes contain gypsum quarried in the province.
Gypsum is 21% water at the molecular level and is therefore fire-resistant. This is the main reason why it is used in wallboard: safety.
The Ottawa Brook quarry in 1926
