Lapidary material from the districtincludes the most diverse collection of datolite colors. The datolite is foundas nodules of massive, finely crystalline, material. The nodules usually do notshow any datolite on the surface and are recognizable primarily due to thesurface 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 porcelainhabit of datolite is also found as a vein filling material, but is difficult torecognize on the mine dumps. The commonestcolor 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 themineral 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 theNorth and West shores of the Keweenaw peninsula. The classic Lake Superior agateis a brown/red and white finely banded agate, although many other types arefound in the area. When looking on the beaches ( especially when the rocks arewet), the agates display a more translucent (like caramel candy) luster than thevolcanic rocks which make up the majority of the beach rocks. The specimensbelow are all cut and polished.