Tony,
There are certain rules which I follow when choosing a stone to carve. The
amount of time it has been left to the elements has never been a
consideration.
1. Never choose a boulder because you don't know what is inside. It may
contain unseen giant flaws, strange colors, who knows what.
2. Know the region where the marble was quarried. Certain marble types will
carve easily. Marble is composed of three grains running in three different
directions. If the strength of the grains is equal or close to equal the
carving will go well. If you have a hard grain in one direction, round a
curve and encounter a soft grain, you have difficulty.
3. Choose a stone that has been saw cut on at least one side. You can look
for flaws, see the color more accurately, and get fewer surprises. Always,
consult an experienced person in stone quality if you are buying a large piece
of marble. They can apply a tuning fork to the marble and tell you the
quality. You may need to pay for this service but it may prevent a 9 ton
mistake.
4. The rule of thumb is that the whiter the stone, the easier to carve. The
darker the marble, the harder.
Marble is formed by compression. Even a stone which is considered reliable for
carving such as Carrara Marble may have come from a bad area of the mountain.
Before you put much effort and time into marble, you must be very cautious.
Susan
