# Mineral Hardness Color Transparency Crystal System Probability See More
1Covellite1.5 - 2.0Indigo-blue or darker, inclining towards blue-black, often iridescent with purplish, deep red, and brassy-yellow reflections.OpaqueHexagonal0.004
2Melanterite2.0Colorless to white or green, also greenish-blue to blue with increased Cu content, colourless to pale green in transmitted light.Translucent, OpaqueMonoclinic0.003
3Nontronite1.5 - 2.0Green, olive-green, yellow-green, yellow, orange, brownMonoclinic0.002
4Ktenasite2.0 - 2.5Blue-greenMonoclinic0.002