TESTMARK Laboratories Ltd. We are a Canadian-owned, privately-held company operating in Garson, ON, Sault Ste. Marie, ON and Mississauga, ON. The company began laboratory operations in 1998, and is the largest independent commercial Laboratory in Northern Ontario with over 35 full time staff, including scientists with advanced degrees in Analytical Chemistry. The company provides organic, inorganic and biological testing to all interested parties in the environmental, industrial and government sectors.