1) Sulfide mineral 
Chatkalite is an copper, iron, tin sulfide mineral with formula Cu6Fe2+Sn6S8. It crystallizes in the tetragonal crystal system and forms as rounded dissemations within tetrahedrite in quartz veins. ==Physical properties== Chatkalite can have sizes ranging from rounded grains of about 100 micron when found within a tetrahedrite. It has a metallic l...