About the stone

The Shed - - Stone Carving -

Oa­maru stone, some­times called ‘white­stone’, comes from a 40m thick de­posit of lime­stone 5km in­land from the North Otago town­ship of Oa­maru. The dis­tinc­tive creamy-coloured stone is bry­ozoan lime­stone, which is made up pre­dom­i­nantly of cal­cium car­bon­ate (90 per cent) with trace chem­i­cals in­clud­ing alu­mina (1.5 per cent), iron ox­ide (0.5 per cent), and sil­ica (0.5 per cent). The sed­i­men­tary rock is soft when first quar­ried but hard­ens on ex­po­sure to air. This, along with its uni­form gran­u­lar tex­ture, makes it ex­cel­lent for sculp­tural and or­na­men­tal pur­poses. As it is por­ous, it must be sealed if out­side. “If it stays wet for a long time, the stone will go mushy and be­gin to break down,” says Shaugn. The stone has been quar­ried at var­i­ous sites along the de­posit since the 1860s, but Park­side Quar­ries at We­ston, which opened in 1906, is the only re­main­ing op­er­a­tion. It was orig­i­nally sliced from the hill­side us­ing a steam-driven chain­saw mounted on rails but these days is cut with hy­drauli­cally op­er­ated 3m tung­sten-tipped cir­cu­lar saws. The stone has been widely used as a build­ing ma­te­rial in Oa­maru, but also fea­tures on prom­i­nent build­ings around the coun­try, from Dunedin’s his­toric rail­way sta­tion to the Auck­land Town Hall. Mount Somers lime­stone, found in mid Can­ter­bury, is denser than Oa­maru stone but its treat­ment is the same for carv­ing. “You use the same tools but ev­ery­thing takes two or three times longer,” says Shaugn.

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