Really? I am curious about your expertise that you would know this. According to this articale:
The tiny village of Ilakaka, Madagascar had barely 40 residents before 1998. Then, a large deposit of sapphires was discovered along a nearby riverbed, and caught the eye of some Thai businessmen in the gem trade. Word got out, and Ilakaka swelled to tens of thousands of residents - the center of a sapphire boom, today the source of nearly 50% of all the sapphires in the world.
*** I am not sure how 50% of the market of the world and they are low grade? DO you have some where it shows that they are low grade coming out of this region? "Most"....JMHO~!