The production of minerals contributed less than 1% to the GDP. Mineral production in 2001 included cement, 1.1 million tons; common clays, 420,000 tons; sandstone, 3.3 million tons; and limestone, 900,000 tons. Diatomite, lime, pumice, silver, marine salt, crushed stone, and sand and gravel were also mined in 2001. Except for clays, fertilizers, and lime, most mineral commodities were produced for domestic use. Canadian and US companies were involved in a number of gold and silver exploration and mining operations. The open-pit heap-leach Bellavista gold project—projected to produce 1,866 kg per year during its projected 7.3-year mine life—became the first mining project approved as a free trade zone, with 100% exemption from import taxes and duties on raw materials, supplies, machinery, and equipment, as well as income, export, local sales, consumption, excise, and withholding tax exemptions. The 74,700 kg Cerro Crucitas gold project anticipated receiving final approval in 2002.