Five years after the market for roofing slate appeared insatiable, thirst for the material abated not to revive until after 1900. Technical advances, economic conditions and architectural taste all seemed to be at play in the decline, illustrating the difficulty of isolating factors influencing the use of construction materials.
A great reduction in the price of copper about this time may have induced the federal government to reconsider the advantages metals offered for residential roofing in light weight, incombustibility and easy installation. After 1888, Public Works specifications began to call for galvanized iron and copper roofing rather than slate.
Centre Block in 1890 and also covered the Langevin Block constructed between 1888 and 1890. Reaction to the picturesque forms of High Victorian Gothic and Queen Anne Revival architecture also set in during the 1890s. The eclecticism of the era continued in the parade of Beaux-Arts, Chateau and Romanesque designs that began to appear in Canadian cities, but the former polychrome effects in roofing were now passe. Many architects and builders working in these styles found metal and other roofing materials acceptable where hitherto only slate had been able to provide desired patterns and natural variety of colour. Besides the rivalry of other materials and changing taste, world recession contributed to the decline in the use of roofing slate in the 1890s.
From a high of 200 men in 1893, the workforce of the New Rockland Quarry was reduced to 90 in 1897. Canadian production temporarily stopped in May 1900. Although it resumed a year later, the quarry never again supplied more than a third of the Canadian consumption of roofing slate.