ABSTRACT: Izmir is the third biggest metropolitan city in Turkey with a population more than 4 million. Thequarries which presently supply aggregate to the ready-mixed concrete plants and cement factories inand around the metropolitan city of İzmir are expected to be closed down in the near future due to theircloseness to the settlement areas and the environmental problems they create. Thus it is necessary tofind new crushed rock areas that will meet the future aggregate needs of the city. It is envisaged that theaggregate needs of the city will be met partially from the Mesozoic aged limestones of the KaraburunPeninsula. In this study, the facies and chemical properties of Mesozoic aged limestones of the KaraburunPeninsula have been investigated and the influences of these properties on the usability as concreteaggregate were evaluated. The results indicated that the most important property affecting the usage ofthe limestones as concrete aggregate is found to be silica content. It affects the purity of the limestonesby causing alkali silica reaction in concrete. Additionally, it has been noted that the clay containingaggregates in the limestones are found to decrease the strength of the concrete.