Found in Malawi, Africa. Glass, quartz, lightning strike??

http://imgur.com/a/vW4wS

Firstly, I thought this was glass. Yet the location it was discovered doesn't really fit..... Found in incredibly poor Malawi in Africa, atop of Nyika Plateau (2300m above sea level), where quartz and other crystals can be found.

Seems a little lighter than a garden rock of this size, the glass is completely free from impurity's, transmits light perfectly, the outside has a yellowy/white grit like texture. When the glass like surface is scratched it is incredibly hardy and difficulty to leave a mark. Where some of it is chipped, it seems to of made a similar fan like pattern to when traditional glass is chipped.