Pure quartz, or “rock crystal” from Brazil ... in the crystal matrix and turn it gray (smoky quartz). Natural quartz crystals usually have a long body with a hexagonal cross-section with ...

Geodes, for instance, are created when mineral-rich water seeps into hollow spaces within rock formations and slowly evaporates, leaving behind dazzling crystals like quartz and amethyst.

Large crystals found in geodes and other rocks are relatively ... and form natural resources such as gold, tin, iron, marble, and granite. Silicates—including quartz, mica, olivine, and precious ...