Richard "Dick" Dietrich of Mount Pleasant is a rock hound. The 85-year-old former Central Michigan University geology professor and dean has been studying all types of rocks, gems, and boulders for 75 years. He can identify a stone before most people can even find a book on geology.

Retired for more than 20 years, he's transferring his vast geologic knowledge into books about stone buildings, houses, and structures. Earlier this year he completed a book detailing every stone structure in Isabella County, more than 200 of them, and now has come to the Straits area to begin his next project, which will catalogue stone birdbaths, monuments, fire-rings, hitching-posts, milestones, landscape accents, walls, chimneys, buildings, homes, and other structures.

"I've already got an outline put together for up here. The structures would be the main part," he said. "There's some fantastic stone walls up here, too."

He originally came to the Straits area to spend time with family. His daughter, Krista, and her husband, Bob Brown, live in St. Ignace. Mr. Dietrich decided to write this book based on stone structures he had seen while just driving around. He already has a list of more than 20 structures he wants to photograph; he will also record historical information about them.

Mr. Dietrich plans to take photographs of stone structures in St. Ignace, Mackinaw City, Mackinac Island, Cheboygan, Brevort, Cross Village, Hessel, Pointe Aux Chenes, and everywhere in between. He wants residents with stone structures in those areas to be aware that he may be walking through their property during the next several weeks to snap photographs. This way, he said, they're not alarmed if they see a stranger photographing their property.

But not every stone structure in the Straits area will be looked at. He is looking for structures made with naturally occurring cobblestones and boulders. Properties with limestone or quarried rocks, he said, are off his radar.

"I'm dealing with the cobbles and boulders because they've been carried into the area by glaciers," he said. "There's an awful lot of things here that are the other type of stones, but to me, that's dull; it's all the same stuff. Whereas boulders, you can look at a place with cobbles or small boulders and it's going to have 25, 30, or maybe 100 different types [of stone]. That's where the fun comes in. That's what's fun for me."

Each structure Mr. Dietrich photographs will be catalogued in the book as well as on his Web site, www.cst.cmich.edu/users/dietr1rv. He plans to photograph structures in Mackinac County this month and in November, and conduct research through the winter. Next spring and summer, he said, he will search stone structures in the northern Lower Peninsula. The book will include a map locating every structure photographed, and an appendix identifying the specific types of rocks.

He said once his book is complete, it will be available for nonprofit organizations to publish as a reference book, but not to be sold for profit.

"If anybody like a historical society wants to publish it, they're welcome to do it," he said. "I'm not in it for the money. I haven't made a penny on [his last book about Isabella County], and I don't want to make a penny on it."

Mr. Dietrich has written more than 20 books in his career, most of them textbooks, and conducted geologic research on every continent except Antarctica.

"Geology is great from a travel standpoint. Along with the fact that wherever you go, you see things that are geological," he said. "Some people find what they really like and they do it. I was lucky."