Lapidary material from the district includes the most diverse collection of datolite colors. The datolite is found as nodules of massive, finely crystalline, material. The nodules usually do not show any datolite on the surface and are recognizable primarily due to the surface texture of the nodules (they look like the surface of cauliflower). These nodules have grown in gouge zones of small faults in a clay matrix. The porcelain habit of datolite is also found as a vein filling material, but is difficult to recognize on the mine dumps. The commonest color is white. Also occurring is blue ( colored by oxidized copper compounds), red, orange, green, mauve, brown, black, and yellow.

Seaman Museum datolite page.

Chlorasterite is a massive, but polishable variety of the mineral pumpellyite. It is the official gemstone for the state of Michigan. Seaman Museum display - largest sample is 4cm.

Lake Superior agates are found on several beaches on the North and West shores of the Keweenaw peninsula. The classic Lake Superior agate is a brown/red and white finely banded agate, although many other types are found in the area. When looking on the beaches ( especially when the rocks are wet), the agates display a more translucent (like caramel candy) luster than the volcanic rocks which make up the majority of the beach rocks. The specimens below are all cut and polished.