Reflectivity and Hardness of Chromites

Abstract

Chromite is an ore mineral possessing the highest hardness (VHN) and very low reflectivity among the common ore minerals. Though the ideal chemical formula of chromite is given by R²⁺OR³⁺₂O₃, chromites in nature show a noticeable substitution variation between chromium and aluminium trioxides.
It is thought that the degree of substitution variation is reflected on reflectivity or hardness of the mineral. Therefore, EPMA analysis for the collected chromites were carried out first. For this study Leitz MPV Compact Microscope Photometer and Leitz Micro-Hardness Tester were used for the reflectance and hardness measurements respectively. Samples of podiform chromites were collected from the Hidaka district, Hokkaido and the Chugoku-Shikoku districts, southwestern Japan, and from the Fethiye mine, southwestern Turkey. Stratiform chromites from the Merensky Reef of Bushveld Intrusion were also provided for this study.
The relationships between chemistry, reflectivity and hardness of chromites were investigated synthetically, and interesting mutual relations among these have been disclosed.