Arsenopyrite

San Antonio Mine (San Antonio el Grande Mine), East Camp, Santa Eulalia District, Municipio Aquiles Serdán, Chihuahua  Mexico

Specimen size: 2.7 × 1.8 × 1.3 cm = 1.06” × 0.71” × 0.51”
Main crystal size: 1.4 × 0.5 cm = 0.55” × 0.20”