Purpurite-Heterosite

Purpurite and heterosite are manganese-iron phosphate minerals that form a solid solution series, where purpurite is the manganese-rich end member and heterosite is the iron-rich one. They form a continuous series, meaning specimens can have varying ratios of iron (Fe) and manganese (Mn). It’s often difficult to distinguish them visually in the field, requiring chemical analysis (Fe-Mn ratio) to confirm if a specimen is purpurite or heterosite.