any instrument for determining with precision the degree of hardness of a substance, especially a mineral, as by measuring the pressure necessary to pierce or scratch it.
Origin of sclerometer
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
an instrument that determines the hardness of a mineral or metal by means of a diamond point
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012