Raw and Natural Crystals and Rocks for Collecting Sorting Tumbling Polishing Gem Mining Cabbing Wire Wrapping and More! Each 4-pound bag contains of up to 40 unique and different stone types measuring on average 1-3 Manufacturered by Kolt Mining. Includes a 64-page Spotters Guide for Rocks and Minerals and identification card. The scientific study of rocks is called petrology which is an essential component of geology. STEM Recommended for Ages 6+ Assorted Premium Rough Rock Variety from Brazil Madagascar and India (rocks in picture are wet and have been washed to show their unique features).