October 13, 2014
Minerals come in a rainbow of colors. Sometimes, mineral color is a result of the mineral’s composition. For example, azurite is always blue. Other times, mineral color is a result of small quantities of trace elements or structural defects in the mineral. For example, quartz, one of the most common minerals, is most often clear or white but can be other colors such as rose pink, yellow, purple, and even brown. The rose pink color, for example, is a result of trace amounts of titanium, iron, or manganese. Thus, it can be difficult to impossible to identify minerals by color alone. Other physical attributes, such as hardness, density, shape, and luster, must also be considered to properly identify a mineral.
I visited the Smithsonian Natural History Museum in Washington, DC, back in June 2014. The museum has very impressive displays of rocks, minerals, and gemstones. I spent a few hours looking at the displays although I unfortunately found myself in the midst of throngs of summer visitors. Despite the crowds, I enjoyed looking at all of the mineral displays, and I even managed to take a few halfway decent snapshots. However, the displays are much more impressive in real life.
This week’s “Monday Geology Picture” shows a mineral rainbow display at the Smithsonian Natural History Museum. What a wonderful display of red-orange-yellow-green-indigo-violet minerals!