I discovered quite a few samples of Prehnite mixes that I found in the Keweenaw. All of these came from my cabochon collection, so I decided, this month, to follow up my blog on Patricianite in October, by showing you a small sample of what can be found on the beaches and in the hills of the Michigan’s Keweenaw Peninsula. Out of all the rocks and minerals in the Keweenaw, these little Prehnites are one of the most common treasures. On the beaches they wash in as pastel pebbles standing out against a rocky background of reds and browns. In the forest roads, quite often, Prehite’s have a white crust ( a little secret Rockhounding tip) with no clue as to what is hidden under the crust. I just pick them, take them home, and grind off a bit of crust. Maybe there’s treasure under the crust, maybe not.
I do not own expensive scientific instruments like a Scanning Electron Microscope (SEM), so I do not have the capability of analyzing every Prehnite mix I find, but I can tell you there is no limit to Nature’s recipes in regard to these beautiful pastel Treasures.
You may know that in the past, because of their resemblance to the Zeolite Thomsonite, this variegated, sometimes eyed Prehnites, were thought to be Thomsonite. Research done at Michigan Tech revealed that these “U.P. Thomsonites” were substantially Prehnite Mixtures. The old time rockhounds still refer to these as U.P. Thomsonite.
Sometimes you feel like an eye, sometimes you don’t. I suspect the suspect on the left may include Datolite.
Lovely pastel greens and pinks (color caused by micro-copper inclusions) dominate U.P. Thomsonite.
The patterns are so varied–collecting is fun and addicting!.
Notice the brachiation (various spellings) in the right hand stone.
Jewelry grade