Indentation hardness
Hardness measurements quantify the resistance of a material to plastic deformation. Indentation hardness tests compose the majority of processes used to determine material hardness, and can be divided into two classes: "microindentation" and "macroindentation" tests. Microindentation tests typically have forces less than . Hardness, however, cannot be considered to be a fundamental material property. Classical hardness testing usually creates a number which can be used to provide a relative idea of material properties. As such, hardness can only offer a comparative idea of the material's resistance to plastic deformation since different hardness techniques have different scales.
Cupules
Typically cupules were created by direct percussion, i.e. using hand-held hammer-stones. Replication studies have shown that the time required for their production varies greatly, depending on the rock type. It can take one minute to create a 12 mm deep cupule on weathered sandstone, but 45,000 and 60,000 hammer-stone strokes on unweathered quartzite. The resistance of a rock to kinetic impact is determined by its hardness, toughness and strength. Hardness, in this context, is a complex articulation of several factors, essentially a measure of how resistant rock is to various kinds of permanent shape change when a compressive force is applied to it. These factors include scratch or abrasion resistance (Rosiwal scale), toughness, strength, ductility, indentation hardness (measured by the Brinell scale and expressed in BHN, or measured by the Vickers test and expressed in kg/mm²) and brittleness factor. Abrasion hardness, indentation hardness and brittleness factor (ratio of the uniaxial compressive strength and the uniaxial tensile strength) combine to determine the “composite hardness index” "θ", which governs the production coefficient "ρ":