Sri Lanka's mineral extraction industries include gemstones, mining, graphite, kaolin, quartz, apatite, silt, clay, and excavation of beach sands containing monazite and ilmenite. Among these, gem mining is the most important because it produces high-end gemstones such as ruby, sapphire, topaz, and other semi-precious stones that are sold in foreign markets. Monazite, ilmenite, and graphite exported in semi-processed form contribute only a small portion of the country's foreign earnings.The Central Bank of Sri Lanka oversees all banking and currency-related issues. Until the late 1970s, commercial banking was virtually monopolized by the two state-run banks, People's Bank and Bank of Ceylon. Following the liberalization period. It enabled the establishment of numerous privately owned commercial banks as well as the overall expansion of the banking industry. Similar patterns have been observed in other commerce-related sectors such as wholesale trade and insurance. Increased private sector participation in commerce and industry resulted in active stock market trading in Colombo.