Slates used in many areas as roofing material for ordinary constructions and in pavements also fall in category of building stones.

Use of limestone as facing stones, even if quite strong, should be avoided in situations where- air is polluted with industrial gases, such as in industrial towns; along sea coasts where sea-water-rich winds can attack m directly.

Rock mechanics deals essentially with behaviour of rocks under applied force fields in natural as well as in laboratory conditions. Rock mechanics has developed at such a fast pace during last it has already become a compulsory part of advanced civil engineering practice.

Basalts are dark coloured basic igneous rocks that have been extensively used as road materials in areas of ir occurrence. The rock is generally characterised with a crushing strength between 2000-3000 kg/cm2 and also with great toughness.

Sandstones and limestones may show varieties as high absorption values as 10% or more. Selection of such highly porous varieties of stones for use in building construction, especially in moist situations, would be greatly objectionable.

Abrasive is more a qualitative than quantitative property and may be broadly defined as resistance, which a stone offers to rubbing action of one kind or anor.

Compressive strength is also sometimes referred as crushing strength of a stone and may be defined as maximum force expressed per unit area, which a stone can withstand without rupturing.

By workability of a stone is understood ease in effort and economy with which it can be extracted from its natural place of occurrence and finally given a proper shape called dressing.

Transverse strength is defined as capacity of a stone to withstand bending loads. Such loads are only rarely involved in situations where stones are commonly used.

Hardness is defined as resistance of stone to rubbing and grinding action under wheel of traffic as also due to mutual attrition. It is known that aggregates of roads and pavements undergo repeated shaking movements under traffic load.