Information & Granite Selection
Granites Are Not The Same.
& Metals Inc. produces granite products from several types
of granite, depending on the customer's needs. Government
tests have shown that fine-grained black granites are
stronger, denser and less absorptive than other granites.
For this reason precision machine bases, air-bearing
surfaces and accessories are best made from black granite.
Since black granites contain no crystalline quartz and
little mica, they have a very high modulus of elasticity,
producing superior load-carrying capacity. Black granites
have uniformly fine textures and tight porosity,
characteristics which make this igneous rock extremely
resistant to water absorption or warping from humidity. The
superior stiffness of black granites is highly desirable for
surfaces where accuracy and stability are essential.
Lighter-colored gray granite (quartz diorite) is excellent
for large surface plates and machine bases subject to heavy
wear, both because of its high quartz content and lower
price. All the granites we use have been carefully measured
to establish the modulus of elasticity, allowing us to
comply with federal specifications and user requirements.
Our knowledgeable staff can assist you in choosing the best
granite for your product, based on considerations of
uniformity of surface, accuracy, deflection under load, type
of use and price.