rare
prehnite
green bubbles · not a greenstone turtle
The tell
Pale green and botryoidal, a crust of rounded bubbles frozen onto basalt. That bubbled surface is the tell: bubbles, not turtle-back. Greenstone segments into a mosaic of tiny scales; prehnite just swells and stays smooth.
The color runs bottle-green to nearly white, with a soft waxy glow when it is wet. Calumet Waterworks and Esrey Park are the two named spots, both up the Keweenaw.
What it gets mistaken for
- isle royale greenstone
- datolite
- thomsonite
- epidote
- green beach glass
The facts
- also calledgreen bubbles · not the greenstone turtle-back
- age~1.06 billion yrs
- where it turns upCalumet Waterworks & Esrey Park
- the field markpale green bubbles · harder than a knife
- on the chartrare · 250 stickers ever
Put it on the shelf
Every stone on this chart is drawn and kiss-cut at three inches. The rarer the stone, the fewer exist: only 250 prehnite will ever be printed, then the run is retired.
10% of every order goes to northern Michigan animal shelters.