Apr 20
Final piece this week — a specular hematite cluster from Inner Mongolia. Hematite is iron oxide (Fe₂O₃), and in this form — where it grows as thin, parallel metallic-gray crystals in a fanned or rosette pattern — collectors usually call it "specularite." The trick of hematite is the streak test: even the blackest, shiniest specimens leave a rust-red streak on unglazed porcelain, because inside that iron is oxidized. Same compound as the Martian surface and most of the red pigment humans have used for tens of thousands of years.
