May 6
Dioptase from Congo, on the iconic tan host matrix. The emerald color you're seeing isn't a treatment or a coincidence — it comes from copper cyclosilicate chemistry. Cu²⁺ ions sit in 6-fold coordination with silicate, absorbing wavelengths in a way that produces this specific deep saturated green. Same Cu²⁺ ion as malachite, but in a different crystal environment, hence a very different green. Most dealer-grade Congo dioptase originates in the Mindouli area, where the host rock is the honey-colored matrix you see here. The combination of crystal habit, color saturation, and matrix character is locality- specific. Specimen from My Mineral Box.
