It is the colour of local sandstone, but much much denser.
Volcanic was suggested as there are some shiney bits which might be mica but I thought were more like quartz.
I have emailed Newcastle Uni, if they show real interest I'd like to know which type too.
Stan's idea about it coming from Scotland was based on it being perhaps metamorphic.
.o0O0o.
PS for lottery numbers why not use the 6-figure grid ref!!!!