Back in 1979 at a place called Tomahawk Creek near to Rubyvale in Central Queensland, Australia, a 2020 carat (404gr) yellow gem sapphire was discovered.
The story alleges that a local boy, on his way home from school, spotted the gem exposed in loose rock in waste from a pit being dug.
The uncut stone is one of the largest and arguably one of the best ever found in Australia. The striped yellow and blue growth margins giving rise to the "tiger" in the Tomahawk Tiger name, though to me it does look more like the abdomen of a very large wasp!
It is believed that the blue colouration has been caused by differing concentrations of titanium as the crystal formed over time, These changes must have been fairly consistent to give such a regular pattern.
The history of the stone out the ground has a familiar human side, it was stolen shortly after discovery to be recovered to the owner in 1986, then sold privately into the USA for over $1 million in 2010.
Colour zoning in sapphire (corundum) is unusual and not unique to Rubyvale in Queensland.
Here below are some pictures of a much smaller example from Ambondromifehy, Antsiranana, Madagascar. This little 12mm crystal also comes from alluvial diggings and was collected in 2005.
Thanks to Aymeric Longi for pointing out the similarity between ours and the Tomahawk Tiger crystal.
Not quite as yellow as the Tomohawk Tiger, it is also not likely to change hands (here) for $1 milliion!
