Salt, gypsum, kaolin and construction materials were produced in 2008 and only salt and gypsum exported. Salt production increased by 350 per cent in 2008 but the country is still a relatively small producer (16th in Africa). Eritrea reportedly has significant mineral resources including asbestos, baryte, copper, gold, iron ore, lead, zinc, silver, magnesium, potash, talc, possibly petroleum and natural gas. Several high-grade polymetallic volcanic massive sulphide (VHMS) deposits have been discovered in recent years (e.g. Adi Nefas, Debarwa, Emba Derho, Bisha) and mining is expected to begin in the near future although exploration and mine development is impacted by political tensions between Eritrea and Ethiopia following independence.