Minerals of the Adirondack Highlands
When continental plates collided with proto-North America during the Grenville Orogenic Cycle around 1.3 to 1 billion years ago, they formed a long chain of mountains which includes the dome-like uplifted region called the Adirondack Mountains.
The Adirondack Mountains are morphologically and geologically divided into the Adirondack Highlands and the Adirondack Lowlands by a wide zone of deformation called the Carthage-Colton Mylonite Zone. The Adirondack Highlands contained igneous rocks such as anorthosites, gabbros, and granites, as well as, sedimentary rocks and iron and titanium deposits. All of these rocks were metamorphosed 1090 to 1050 million years ago to granulite facies at a depth of around 25 kilometers and a temperature of 750Ãï¿½Â° C. A complex interaction of the igneous, metamorphic, and hydrothermal geological processes shaped the Adirondack Highlands and generated a plethora of minerals. The finest examples of these minerals from the State Museum's collection are featured in this display case.