Black Sea coast line is a hazardous region especially in winter due to the dominant wave action. Therefore, rubble mound breakwaters protected with armourstone used as ship shelters are vital structures especially for the fishermen. The deterioration of the armourstone with time in the form of abrasion and disintegration may result in the failure of the breakwater. In this study, the properties of the armourstone taken from an andesite quarry and used in the Hisaronu rubble mound breakwater were studied both in field and laboratory in order to assess their qualities and long-term durabilities. Based on the in situ observations and laboratory tests, the andesite is found to be generally marginal rock. CIRIA/CUR, RDIs, RERS and Wet-Dry strength ratio classifications are in good agreement with the in situ observations and the results of the laboratory tests. However, RDId, Average Pore Diameter and Saturation Coefficient classifications cannot correctly predict long-term durability of the armourstone. Field studies reveal that block size of the andesite in the quarry increases with depth due to the increase in spacing of the cooling joints of the rock.