This paper deals with the possibility of using the Schmidt hardness test, which does not require much preliminary preparation and is easy to perform, in the production of commercial blocks in a quarry. Previous recommendations for Schmidt hardness testing of rock materials were specifically related to tests performed for geomechanical purposes. They also referred mostly to smaller samples, but testing of commercial blocks has some special features, mainly because they are large samples for which practically larger areas must be tested. This paper presents the testing methodology in terms of the number and position of hammer strikes on a commercial block, as well as the application of corrections to the test results in terms of the way the blocks are cut. The tests were conducted on natural stone blocks from the Kanfanar-South quarry, which is characterized by limestone rocks. The test results show that the test methodology can be applied in quarries with similar geological structure and natural stone mining methodology.