Many people are discovering the fun of collecting rocks, minerals, and fossils. There are millions of “rockhounds.” Michigan has many beautiful beaches and shorelines to stroll along where a stone may 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) crystallize below the Earth’s surface and cool slowly, forming large crystals. Extrusive igneous rocks (volcanic) erupt to the Earth’s surface and cool quickly, forming small crystals. Earth’s upper crust is 95% igneous rock. In Michigan, places to find igneous rocks include Horseshoe Harbor in Copper Harbor and the 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. This causes chemical or physical changes that form a new rock. Metamorphic rocks in Michigan are mostly found in the western Upper Peninsula, but fragments can be found in almost any gravel pit due to glaciers carrying 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, including Pictured Rocks in the Upper Peninsula, Arch Rock on Mackinac Island, and Turnip Rock in Port Austin. Michigan also has the world’s largest limestone quarry, which is a 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 as well as sideways. Kona Dolomite also has the unusual nickname of "Moose Blood." The most interesting fact about Kona Dolomite is that it is one of the oldest rocks found on the planet, between 2.1 and 2.2 billion years old, and formed from some of the earliest 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 at rock #26 for what remains.
Don't forget those favorite points and, if you like, post a picture with your favorite rock and/or the Pure Michigan sign!
Extra Credit: Grab some SWAG!! Find our other geocache “MDOT-Party "OWL" Night, Sleep "OWL" Day.”
If you happen to visit while the MDOT Pure Michigan Welcome Center is open, make sure to pick up 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.
Current lobby hours for the MDOT Monroe Welcome Center are Tuesday-Saturday from 8 a.m. to 4:30 p.m.
The Pure Michigan Rock Garden and the Rest Area are open 24 hours a day and are in a lit area.
If you like our cache, please remember to give us those favorite points!!