It might be that the super-hardwood is ipe (ee-pay). It is the most dense woods that are more commonly available. Scales judging the density/hardness of wood species will say that the burn rate of ipe is about par to concrete!

If any of you have dabbled in the world of wood, you will find that it is easy to drive a nail (say, 8d common) into spruce. It is the most common of domestic wood species and rates at about 600 Janka. A Janka (similar to Newtons) is a test to see how much force must be used on a .445" steel ball to embed it half way into the desired wood. The higher the Janka number, the denser the wood, and makes it harder to cut, nail, etc... Domestic Red Oak and Ash, especially the harder NorthEastern species, will rate in the 1300's. If any of you have tried to drive an 8d nail into oak, well, good luck on keeping the head straight. Ipe rates about 3800 Janka- almost three times the hardness of Red oak, rarely contains a knot and is pretty much non-absorbant.

Ipe would really make a good tie, but doesn't come cheap. My latest hot sheet from my supplier tells me that I would sell it at $6.00US/BDFT (12"x12"x1"). That would be about $35.00US per/ft
for an 8"x8" rough. Calculate it for an eight foot piece, and presto!- $280.00US/tie. That's $14000.00US of Ipe to replace a 100' section of ties. Add labour, transportation, tools....etc...

almo