from The Century Dictionary.
- noun An impure variety of compact prehnite, forming nodules in the amygdaloid of Isle Royale, Lake Superior. It has a delicate green color and radiated or stellate structure, and takes a high polish.
Sorry, no etymologies found.
Some gems, such as the chlorastrolite, thomsonite, and agates of Lake Superior, are gathered on beaches, where they have fallen from rock which has gradually disintegrated by weathering and wave action.
Thomsonite in pebbles occurs with the chlorastrolite at Isle Royal, but finer stones are found on the beach at Grand Marais, Cook County,