Henan's reserves of molybdenum, marble, trona, asbestos, aluminium, natural gas, cesium, bauxite, coal, perlite and refractory clay are among the largest in China. The province 's coal output ranks third in China, after Shanxi and Shandong. The rich oil and gas reserves in the Nanyang Basin are currently being exploited. Zhongyuan oilfield is one of the largest oilfields in the country. Half of China's aluminium oxide output comes from Henan. Henan's bauxite reserves are the second largest in China. Henan is an agricultural province, with grain production ranking second only to Shandong. Major agricultural products include wheat, beans, ramie, oil and cotton.