Could this be a carbonado diamond or a lonsdaleite?

Hi guys!
My friend found a rather found a rather intriguing rock.
This very mysterious rock or stone (not really sure what to call it) was found in Espírito Santo, Brazil. It

It is extremely heavy for it´s size, and hard. What intrigues me the most is the fact that we try to cut it with an electric saw, and it wore the saw out but it did not break or barely scratched the surface of it!

According my research the two worlds hardest materials are: the diamond, as we all know it, and the lonsdaleite, also called the hexagon diamond.
Could this be a rough carbonado or a lonsdaleite?

Relevant data:
- When immersed in water, it become very shinny: even those greyish or brownish sections become very glittery and sparkly in beautifull earthy colours;
- Weight: 3,735 Kg;
- Measurements: 49 cm around its longest side and 39 cm around its shortest side;
- Does not attract a paper clip, does not react to a magnet or to a compass at all;
- Found in Espírito Santo (just next to Bahia, Br);
- Under hot sun, it stays cool all the time.

If you are interested in seeing the specimen please email me! =)

[email protected]

Many thanks!