 Most of the gumfields were in Northland , Coromandel and Auckland , the site of the original kauri forests . Initially , the gum was readily accessible , commonly found lying on the ground . Captain Cook reported the presence of resinous lumps on the beach at Mercury Bay , Coromandel , in 1769 , although he suspected it came from the mangroves , and missionary Samuel Marsden spoke of their presence in Northland in 1819 . 
