In 1712, building began on the construction of the library building. Records show that a type of limestone was used, extracted from a quarry in Palmerstown, located some 8 km to the west. Patrick Wyse Jackson, curator of the Geological Museum at Trinity, assessed the Old Library in 1993, and made the following observations:

"The Old Library was built between 1712 and 1732... The lower storey is built of muddy, well-bedded Calp Limestone, cut into regular rusticated ashlar blocks, which were quarried at Palmerstown... This rock is quite fossiliferous and contains tiny cubic crystals of iron pyrites or 'fool's gold'... The Calp has weathered to a pleasant, warm, brownish colour which contrasts well with the grey Ballyknockan Granite of the upper storeys. Originally these levels were faced with white St Bees Sandstone from Whitehaven in Cumbria, but this disintegrated quickly and all but the carved cornice was replaced."