WHEN COLOR FAILS YOU: INVESTIGATION OF MALACHITE AND RELATED MINERALS

The Department of Earth Sciences at Kent State University at Stark strives to include practical skills and research training in most undergraduate course offerings. In the sophomore-level Earth Materials I, students conduct research on an unknown mineral. The inclusion of an independent mineral project shows students the practical benefit of learning mineralogy which can seem esoteric to beginning majors. For this study, the mineral properties of malachite and related minerals were investigated. Two lab specimens that were labeled as malachite were compared, and upon cutting the specimens it became clear that one of them was not malachite due to its internal bright blue color. In order to determine the identity of the unknown mineral, several properties were tested in hand sample, under SEM/EDS, and in thin section. Both minerals had the same hardness of 3 ½ and produced a streak the same as their bulk color. EDS analysis showed that both minerals contained high amounts of copper, oxygen, and carbon. The unknown mineral also contained silicon and trace amounts of aluminum and calcium. The SEM displayed that all elements were distributed evenly throughout both specimens. Based on appearance, the identity of the unknown was narrowed down to either chrysocolla or turquoise. The hardness that was identified was too low for turquoise, and the mineral’s streak more closely resembled the color of chrysocolla. Turquoise also does not contain silicon while chrysocolla does, and silicon was the fourth most abundant element displayed by EDS. The study concluded that the most probable identity of the unknown mineral was chrysocolla. This study demonstrated the complexity of mineral identification. Although this experiment highlights just one student’s work, it nonetheless shows that independent research in mineral or rock science may foster a long-lasting interest in studying earth science at KSU Stark.