Amygdaloidal Basalt. This is a natural piece of Amygdaloidal Basalt (Lava Rock with mineral filled pockets) as it was found at a copper mine in the Keweenaw Peninsula of Northern Michigan.
The gas pockets in the original lava rock (basalt) slowly filled with beautiful, colorful crystals. Many sparkle and glitter in the light.
This one has Quartz, possible Calcite and Feldspar in the Basalt host rock.
It is a natural stone, unaltered and unmodified. These polish up very nicely.
See photos for size and weight.