Italian slate is taken from underground, and is relatively soft. It is not suited for outdoor use but is fine for billiard tables. Because it is soft, Italian slate is more flexible. Italy has historically been the billiard industry’s prime source for slate. However, today’s global market has uncovered other excellent sources of prime quality slate.
Mined from open pits, most Brazilian slate is harder than Italian slate. The machining process is more difficult but Brazilian slate is not nearly as sensitive to abuse. It does not bend easily, so storage is less critical. It is also more difficult to break.
Because of its hardness, Brazilian slate is subject to complex gauging and surfacing operations, which in turn produces a very flat surface. Remember that the essential element in slate quality is flatness. Properly processed, both Brazilian and Italian slate are well suited for use in billiards.
Source: Brunswick Billiards