All products in the PETRA lines are made from marble chips bonded together with polyester resin. The percentage of resin is always low and will vary from 4% to 8% of the total weight. PETRA products maintain the characteristics and properties of the original natural stone from which they are produced. Only the resin used to bond the chips and inorganic metal oxides for color are added. Petra products are colored with these metal oxides to insure they are colorfast and will not fade or yellow from ultra violet rays from sunlight.

PETRA products have been used throughout the world for over 30 years and are tested to identify and measure their physical properties. Since PETRA products have a high concentration of natural stone, they are tested using the ASTM tests for marble and granite and listed by the Marble Institute of America. The tests:

C97 Test for Absorption and Bulk Specific Gravity of Dimension Stone
C99 Test for Modulus of Rupture of Dimension Stone
C170 Test for Compressive Strength of Dimension Stone
C241 Test for Abrasion Resistance of Stone Subjected to Foot Traffic
C880 Test for Flexural Strength of Dimensional Stone

PETRA Marble Properties:

Density: average=157 lbs. per cubic foot
Water absorption=.05% maximum
Abrasion Index: average=63.7
MOHS hardness: average=4
Compressive Strength: range=20,250 to 26,600 psi
Flexural Strength: average=3,000 psi
Modulus of Rupture: average=2,700 psi

Additional testing was performed with the following results:

Freeze/thaw cycling: slight dulling of surface after 14 cycles of 48 hr/ea.
Flammability: average=2.55
Toxic gas emission - negligible
Resistance to weather: slight dulling of surface after 100 hours in Carbon Arc Weathometer.
Co efficient of friction: dry - not less than .65.