My answer to Jeff's "boulder splitting" question.

["Ted Schaghy" <ted@zzzzzzzz>]

Jeff,
Igneous rock can be some very tough stuff to work with.  I have seen this
stuff laugh at many a very quickly worn out diamond blades, chisels,
splitters - and shims made of soft metal.  Based on the description you have
provided, I conclude the rock is a solid mass with no "grain" or "layers".
If so, using feathers and shims may not "split" the rock as "splitting" goes
(unless you get lucky), rather it will shatter in uneven chunks and you will
have to drill more holes and continue drilling and shattering the rock down
until you get it to the size and shape you need.  Getting the right pitch on
the shims will help a lot.  In pitching them too far toward the center mass
of the boulder, all you may succeed in doing is getting the shims stuck in
the rock as you strike them.  In pitching them too far away from the center
mass of the boulder you may take off too small of chunks when the rock
breaks, thus you will have to drill and shim a lot more than necessary to
get the job done.  You'll have to experiment a bit and see how the
"splitting" goes and do what works best.  Chances are very good that you
will be hauling the greater part of the removal out of the hole in a lot of
small chunks as opposed to the desired "splitting" of the boulder into just
one or a few large chunks.  But, who knows?  You may strike the rock at a
perfect spot and split it just right.  It is very difficult, if not
impossible sometimes, to tell how this hard stuff is going to behave.  As
far as working your way around the boulder with the shims, I would work all
the way around the rock if I could, striking the shims evenly all the way
around.  If you haven't got the shims, the half moon idea may work just as
well, again striking evenly along your line.

If the rock has "grain" or "layers"(hooray!), chances are good that you can
set the shims in the grain and break the rock continuously and without a
great deal of effort.

There is no easy answer here.  This sounds like a fun job for a dedicated
lover of rock smashing.  It would be very helpful to see a photo of the
rock.

Anyway, let us all know how it turns out.

Happy Rock Wrecking,
Ted