Africa is the world's second-largest and second most-populous continent, after Asia. The continent is surrounded by the Mediterranean Sea to the north, both the Suez Canal and the Red Sea along the Sinai Peninsula to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. Although it has abundant natural resources, Africa remains the world's poorest and most underdeveloped continent, due to a variety of causes. From 1995 to 2005, Africa's rate of economic growth increased, averaging 5% in 2005. Some countries experienced still higher growth rates, notably Angola, Sudan and Equatorial Guinea, all three of which had recently begun extracting their petroleum reserves or had expanded their oil extraction capacity. The continent has 90% of the worlds cobalt, 90% of its platinum, 50% of its gold, 98% of its chromium, 70% of its tantalite, 64% of its manganese and one-third of its uranium. The DRC has 70% of the worlds coltan, and most mobile phones in the world have coltan in them. The Democratic Republic of the Congo also has more than 30% of the worlds diamond reserves. Guinea is the worlds largest exporter of bauxite.