Rockwell Hardness 3 : A numerical value which expresses the resistance of a material to indentation with a small diamond point or a 1/16 in. diameter ball. This correlates directly with strength. (COGWE, SSWID, WLOP)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}