Ruby, Sapphire & Spinel: an Archaeological, Textual and Cultural Study

Until about two hundred years ago, no gemological distinction was made between ruby and spinel. Red spinel and red ruby are not infrequently found together and though gem cutters and engravers noticed and commented on the difference in hardness, the assumption was that spinel was simply an unripe version of ruby. Additionally, ruby and sapphire are both versions of the mineral corundum, distinguished only by color and minute traces of the metal oxides that caused these different colors. Sap...