European standard NBN EN 1926.

This standard expresses the level of pressure/force which needs to be exerted to cause the stone to almost break. This level of pressure is expressed in Newtons per square millimetre (N/mm²) and is adjusted to take account of the surface area of the stone being tested.
This standard can be used to choose stone for particular building applications, where the materials will be exposed to specific load levels (taking account of the safety co-efficient). In this respect, the heterogeneity of the stone plays an important role: some metamorphic stones have a grouping or alignment of their mineral elements in parallel lines or bands. This is known as foliation and the different layers have a clearly different mineralogical composition. This can result in widely differing compressive strengths, depending upon whether the pressure is applied horizontally or vertically.
Indicative compressive strength levels (N/mm²) of different types of natural stone are given in the table below:

Limestone (white stone)	2 to 240 N/mm²
Marble	40 to 230 N/mm²
Granite	80 to 400 N/mm²
Slate	40 to 260 N/mm²

It should be noted that the levels vary widely, even within the same stone type. Yet again, the highest scores (in average terms) are recorded for granite.