Calcopyrite is a mineral composed of copper, iron, and sulfur. In its natural state, calcopyrite has a lustrous, brassy, yellow color, which causes it to sometimes be confused with gold and fools gold (pyrite). It is softer than pyrite and can tarnish to a greenish gray with exposure to weather. Acids cause calcopyrite to tarnish to iridescent red, blue, or purple.
NOTE: The item photographed is similar to the one you will receive. These specimens are approximately 2" in length, and weigh between 2 and 3 ounces each. Region of Origin: Zacataecas, Mexico.