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Enlighten Me: Delaware's hard to find state mineral part of DMNH exhibit

Eurico Zimbres

The Delaware Natural History Museum will be showing off its new display of minerals found in First State starting on May 11.

At the “Delaware Rocks!” exhibit, visitors will see minerals like the Iron Hill iron ore and chert that the Native Americans used to make tools. Cockeysville marble was another mineral used by farmers to fertilize fields, and is the namesake for “Limestone Road” in upstate Delaware because so much of the marble fell off the wagons, turning the road white.

Also on display is Delaware’s state mineral, sillimanite. Also known as fibrolite, sillimanite is a fibrous mineral used to make glass products. But Tom Pankratz from the Delaware Mineralogical Society discovered, sillimanite is rather difficult to find in Delaware.


“I got curious. What is this mineral, what does it look like, where is it found? And surprisingly the answer was: nobody knew," said Pankratz.


He eventually found a large boulder of sillimanite in Brandywine Springs County Park, after several weeks of looking and the help of a stranger's dog.


A former biochemist for DuPont, Pankratz still wanted to pursue science in his retirement.


“As a scientist, you’re the type of person who is just generally interested asking the questions in everything you see and everything you observe. You want to know why things are the way they are and how they came here. And you start asking questions and the questions are endless, you never get all the answers.”

Nonetheless, he finds the pursuit of knowledge rewarding.

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