corundum, color.4, gems

From its vast expanses of cerulean waters to its azure heavens above, our world is dominated by blue, so it is no wonder that the color blue is favored by many across cultures and throughout the ages. The allure of minerals owes much to the perception of color inherent to a particular species or variety. Arguably, whether a person is a seasoned collector or small child, color is what first attracts attention, and quite often its cause is the earliest question posed. Scientific investigations into its nature and articulation of its nuances of hue and quality are the subjects of volumes of literature in both the mineralogical and gemological sciences. Although the present overview narrowly focuses on a selection of blue minerals and aims to do so with some exploratory tools and twists, its concepts also provide insights into the cause of other colors seen elsewhere in the mineral kingdom, as well as in gemstones fashioned from denizens of that realm.