Specimen data for Sillimanite

Tom Mortimer catalog number: 1677

Identification method: XRD analysis by Harvard University, March, 2001, (personal communication Dr. Carl Francis).

Notes: This locality was brought to my attention by Walter Caulkins, whom I met at the Gilsum Rock Swap in 1990. He had a sample of this material and was asking for some identity help. He said it came from a hillside, (Draper's Hill), on his old family farm in Chesterfield, NH. I was intrigued. He offered to take me to the site. We met the following month and he guided me to the spot. The biotite gneiss in the area was loaded with these gray, prismatic, crystals. They are best exposed on the weathered surface, as they are more resistant to weathering that the hosting gneiss. I had originally thought these crystals were Sillimanite. A later XRD analysis by Harvard confirmed my suspicion.