(IDEX Online) - An African farmer has become an overnight millionaire after unearthing two huge slabs of Tanzanite, one of the world's rarest gemstones. Saniniu Laizer, 52, mined the stones, weighing approximately 20lb and 11lb, last week, and has now sold them to Tanzania's minerals ministry for $3.4m.Tiffany & Co first marketed the green, red, purple and blue stone in 1968 under the name Tanzanite, after Tanzania, rather than blue-violet zoisite, its scientific name.It is only found in one tiny area of the country, a four-mile strip near the Mererani Hills in the north, and the biggest find previously weighed just over 7lb.A delighted Mr Laizer said he'll use some of the proceeds to build a school and shopping mall for his community. He has four wives, 2,000 cows and a licence to mine for Tanzanite in an area that is now protected by a perimeter wall to deter illegals.Pics courtesy Tanzania Ministry of Minerals