Granite

Property

Group

Igneous

Common Rock-Forming Group

Siliceous

Composition

Feldspar, quartz, and small amounts mica are the primary minerals of the average granite with minor accessory minerals.

Hardness

Hard

Porosity %

0.24 – 2.3

Density

2.5-2.7 g/cm³

Abrasion Resistance

0.68-4.1 mm

Compressive Strength

137.6-298 MPa

Modulus Rapture

10.45-21.4 MPa

Mohs’ Scale

5 – 7

Absorption %

0.05 – 0.5

Coefficient of Linear Expansion

3.41-6.5 /ºC x 10⁶

Flexural Strength

11-26 MPa

Specific Gravity

2.61-2.98 kg/m³

Weight

2611.26-2707.38 kg/m³

Weathering Characteristics

Generally good to excellent. However, like any other material it has its vulnerable points

Some varieties contain ferrous mineral compounds that when continuously exposed to moisture, will undergo mineralogical changes and being to produce discoloration’s (rust spots) i.e. Rustic Yellow.

Tendencies

Absorbs oils and some will absorb other liquids

Generally not affected by acidic foods and drinks, however, polished granites can be etched by hydrofluoric acid and concentrated acids which are found in some household cleaning products

Some granite varieties when used in water features (spas and fountains); will begin to show signs of deterioration in a few years.

Stone façades need periodic cleaning if good appearance is to be preserved. Dirt deposit includes soot, wind-blown smoke, exhaust from vehicles may affect the surface cleanness.

Staining may be caused by organic growth, urban grime or metal run off. Growths may be treated by toxic washes, metal stains may be more difficult to treat.

Acid Resistance

Acid gases such as sulphur dioxide attack stones containing carbonate material such as calcite and dolomite. This may leads to either erosion causing surface loss or crystalization damages.

Durability Test

Test typically include salt crystallisation, acid immersion, thermal shock, resistance to ageing by humidity, temperature, SO2 action, and resistance to ageing by salt mist.

Colours

Granite is found in more than a hundred distinct colors with varying patterns. Refer to granite resources and names.

Finishes

• Polished
• Honed
• Flamed
• Bush Hammer

Thickness

10-15 mm for internal wall; up to 20mm for floor.

External wall cladding: min 25-30 mm.

Treatment

It’s important to ‘seal’ or impregnating, to ensure it can last to its maximum life-span, i.e. to avoid scratch, water penetration, stains, etc. This usually done before installation on the 5 sides (front, and 4 sides) of the individual cut-panel, or even 6 sides (includes the back side).

When necessary, some treatments should be involved, such as color enhancer, anti slip resin, etc.

Notations

The grain size varies with this stone, from small, medium to coarse. This is important to understand for two reasons:

1. With larger mineral grains or a combination of different grain sizes, the stone has a tendency to be more absorbent
2. Some varieties are composed with a combination of different grain sizes. This natural characteristic is more noticeable in highly polished finishes.

The surface of the stone may appear random. A real tight finish is not completely attainable with some of these varieties of granites. This characteristic is often not detected by viewing small samples of the stoneWith textured exterior installations it is advisable to treat the stone with water and soil repellent. Many of the texturing processes create and exposed micro fractures in the stones surface increasing the absorption factor of the stone.

ASTM C 615 Physical Requirement

* Abrasive hardness values