What is the fine-grained topic of the following text: The first significant discovery of deposits of this great and beautiful, translucent stone was by the American geologist W. Dan Hausel during 1996 in Palmer Creek, Wyoming, and the largest discovered crystal of Iolite is a world record breaking stone, found in Grizzy Creek, Wyoming, measuring over 24,000 carats, and weighting 4.8 kilograms. Only return the topic.
Discovery and characteristics of Iolite stone