More than 350 million years ago, warm, shallow seas covered many parts of North America, including much of the Midwest. During this time period, known as the Devonian era, these shallow waters were teaming with salt water marine life. Fish, mussels, crustaceans, and micro-organisms flourished in the region. In addition to the other sea animals, …
You know those Transition eyeglasses that automatically darken in the bright sunlight then return to normal indoors? The process that makes Transition lenses possible is called tenebrescence, otherwise known as reversible photochromism. Tenebrescence is not a man-made invention developed strictly for sunglasses. It occurs naturally. Some minerals, including hackmanite, have the ability to change color …