The name “mariposite” is also used for rocks. The rocks contain enough particles of green mica to produce a green color. These rocks are metamorphic, have been altered by hydrothermal activity, and they are usually thought to have a serpentinite protolith. The green mica usually accounts for a small percentage of the rock, with the major constituents being quartz, calcite, dolomite, ankerite or barite.

During the California Gold Rush, prospectors learned that “mariposite” was sometimes a host rock of gold. The sight of mariposite as stream cobbles or in outcrops became a well-known sign that gold might be present. This knowledge was later used in the search for gold in other parts of California, British Columbia, Alaska, and other parts of the world.