Karratha stone, being a warm-coloured, dense, strong, abrasion-resistant rock, has a wide range of applications in both horizontal and vertical finishes, where its decorative effects enhance its excellent physical properties.
Steps and paving slabs are especially relevant where the ability of the stone to resist continuous wear and attrition is needed.
The high silica content provides an excellent 'non-slip' surface, whilst strength, colours and textures are features that make it an ideal natural product for walls and 'special features.
Karratha stone is heavy and dense, and easily meets all requirements for bulk specific gravity for sandstone-type building stones.
The chemical analysis, showing over 90% silica, suggests that it should be properly called a Pilbara quartzitic sandstone. There are no deleterious accessory minerals, and iron content is limited to the colouring and bedding plane partings. The absorption and bulk specific gravity tests show a desirable product with low absorption and high density.
» The compressive strength (95.5MPa) is high, and well in excess of any standard requirements.
» The modulus rupture (5 MPa) is greater than that required for a sandstone
» It is resistant to weak solutions and temperature cycles.
» When placed in a laboratory furnace and heated to 600dC, no decomposition or 'splitting' occured, and no adverse reaction or loss of integrity was detected during heating or cooling back to room temperature. Obviously no ignition occured, and therefore there is no evidence to suggest that it poses an unexpected fire hazard.
Karratha stone, being 2.5 times stronger than concrete and with 0.7% absorption rate, becomes water resistant when laid with a 4:1 mortar mix. The application of strand ply is recommended to double the strength of mortar in paving applications. The ratio is one packet to 10m2.