Massachusetts Micromounts

One of the sites I visited with the Wayne County Gem and Mineral Club during the June Massachusetts trip was the large dump beside the Quabbin Aqueduct shaft #10 in Hardwick, Massachusetts.  The 25 mile aqueduct connecting the Quabbin Reservoir to Boston was completed in 1939 and has been a primary source of water for the Boston region ever since.  Rocks excavated from the #10 shaft include the Hardwick granite,  the Monson gneiss, and a number of other metamorphic rocks.  The dump is expansive and although it is becoming overgrown it remains a popular site for mineral collectors.

The almandine garnets in the biotite schist are brightly pink and the bright green epidote coating granite fractures is equally vibrant.  But until I got home I did not know that several of the fracture linings had sub mm-sized, brilliantly purple fluorites resting on the epidote.

Quabbin micromounts: Many of the prizes that remain to be found on the expansive dump are small, in fact they are micromounts. But they are colorful. I took these pictures with a zOrb digital “microscope”. The field of view in each photo is less than 4mm.

The site is best known for babingtonite, a rare calcium-iron-manganese silicate, which is also the state mineral of Massachusetts.  It is also generally found in very small crystals and I had hoped I might encounter some when I cleaned the epidote-fracture coated pieces I carried out and looked at them carefully.  But alas, no babingtonite for me and I must share a picture that Peter Cristofono posted to Mindat in 2010.

1.5 mm babingtonite on epidote from Quabbin aqueduct shaft #10. From Mindat

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