Did you know that many of the largest and most beautiful crystals on display in the museum come from a unique type of rock known as pegmatites? What are pegmatites and what makes them special? At first sight, pegmatites resemble granites, but they have a very diverse range of mineralogy and textures, and unusual chemical compositions. One of the most obvious features that set them apart from granites is their larger grain size. Minerals from granites are 1 inch or less in size, while pegmatites typically contain crystals ranging in size from a few inches across up to 50 feet long! In this tour you'll see examples of pegmatites, learn how they form, and find out how we use some minerals found in pegmatites.

Virtual Tour: Minerals and Gems Gallery
https://naturalhistory2.si.edu/vt3/NM...

More About the Hall of Geology, Gems, and Minerals
https://naturalhistory.si.edu/exhibit...