Jasper County Democrat, Volume 9, Number 11, Rensselaer, Jasper County, 16 June 1906 — The Test of Hardness. [ARTICLE]

The Test of Hardness.

A good many people appear to think that resistance to a blow is a test of hardness in minerals, whereas it is resistance to erosion. Ignorance of this fact led a man not long ago to experiment on what appeared to be a large and unusually clear garnet of rather light red color. He took a hammer to it and smashed it to atoms. A diamond is the hardest substance in the world, yet It may be broken by a tap from a hammer or even a fall on the sidewalk, as It is apt to split along any of the cleavage lines, which are parallel to Its faces. Experts test an undetermined gem first with a file and after with fragment of stone of differing hardness. If it yields to the file, It Is a glass or something no more durable than that.