Many people are discovering the fun in collecting rocks, minerals and fossils. There are millions of “Rockhounds”. Michigan has many beautiful beaches and shore lines to stroll on where a stone can catch your eye. When you begin to collect those stones a “Rockhound” is born.
There are 3 types of rocks:
Igneous Rocks: derived from the Latin word “Ignis” meaning fire. Igneous Rocks are formed from the cooling of magma or lava. Intrusive Igneous Rocks (Plutonic) crystalize below the Earth’s surface and cool slowly which forms large crystals. Extrusive Igneous Rocks (Volcanic) erupt to the Earth’s surface and cool quickly which forms small crystals. Earth’s upper crust is 95% Igneous Rock. In Michigan a few places to find Igneous Rocks are Horseshoe Harbor in Copper Beach and Black Rocks Volcanic Formations in Presque Isle. In our MDOT Monroe Welcome Center rock garden you will see 13 Igneous Rocks, mostly from the Upper Peninsula. A favorite of ours is #5, the Pink Granite, simply because the crystals and color make it so beautiful.
Metamorphic Rocks: derived from the word “Metamorphism” which means change. Metamorphic Rocks are formed when existing rocks are changed by heat, extreme pressure and chemical processes usually while buried deep in the Earth’s surface, causing a chemical or physical change to form the new rock. Usually Metamorphic Rocks in Michigan are restricted to the Western Upper Peninsula, but they can be found in almost any gravel pit in Michigan due to glaciers pulling them south. Most popular in Michigan are the Agates of Lake Superior. In our MDOT Monroe Welcome Center rock garden you will see 7 Metamorphic Rocks from around Michigan. A favorite of ours is #22, the Gneiss. This rock is called a glacial erratic, meaning it is not really from around here but was carried here by a glacier and we find that amazing!.
Sedimentary Rocks: formed when sediment such as minerals and organic matter settles in place. These sediments are cemented together and compacted over time and are often deposited in layers that frequently contain fossils. Sedimentary Rocks form at or near the Earth’s surface but are only a small percentage of the Earth’s crust. Michigan has many sites for Sedimentary Rocks, some are Pictured Rocks in the Upper Peninsula, Arch Rock on Mackinac Island, & Turnip Rock in Port Austin. Michigan also has the world’s limestone quarry of Sedimentary Rock. In our MDOT Monroe Welcome Center rock garden you will see 18 Sedimentary Rocks from around Michigan. A favorite of ours is #23, Kona Dolomite. This rock is found only in the Kona Hills of Marquette County, Michigan. It has bands that run up and down and sideways. The Kona Dolomite also has an unusual nickname of Moose Blood. However, the most interesting fact about the Kona Dolomite is that it is one of the oldest rocks found on the planet. The Kona Dolomite is between 2.1 and 2.2 billion years old and is formed from some of the first life on earth.
Email us answers to the following:
Rock Name and Rock Group for
#3 #11 #15 # 18 # 20 #24
What is the number and name of the stone with the Chain Coral?
Since someone has chipped away part of the Trilobite we wanted to tell you to look in rock #26 for what remains.
Don't forget those favorite points and, if you like, make sure to post your picture with your favorite rock and/or the Pure Michigan sign!
Extra Credit: Grab some SWAG!! Find our other Geocache “Official Pure Michigan-MDOT Monroe Welcome Center”. Don’t worry. Short on time and can’t do the puzzle? The answers are provided under the hint.
If you happen to visit while the MDOT Pure Michigan Welcome Center is open make sure to get a brochure about the Pure Michigan Rocks garden. Stop by our information desk inside to say hello and let us know what you think of our Rock Garden.
The MDOT Monroe Welcome Center Lobby Hours: current Winter hours are 5 days a week Tuesday -Saturday 8am till 4:30pm
The Pure Michigan Rock Garden and the Rest Area are open 24 hours and are in a lighted area.
If you like our Cache please remember to give us those favorite points!!