A tool employed in mineral identification involves rubbing a specimen across a piece of unglazed porcelain. The residue left behind reveals a diagnostic property of the mineral. For instance, hematite, despite its varied appearance, consistently produces a reddish-brown mark on the testing surface.
This method offers a simple, cost-effective means of analysis, particularly useful in field work or introductory geology labs. Its accessibility has made it a standard practice for mineralogists for many years, allowing for a reliable comparison between the color of a mineral’s powder and its bulk appearance, which can often be misleading due to impurities or weathering.
