Welcome to the Cuyuna Range! While mining days have come and gone, this location is just one example where history is still living. Enjoy the view while you visit this Earthcache then take a walk or bike ride to enjoy the Cuyuna State Recreation Area paved and mountain bike trails, toss a line into the lakes for the great fishing, or grab your scuba gear to explore the world "down under".
Portsmouth Mine Pit Lake, referred to today by the locals as Portsmouth Pit, is the deepest lake in Minnesota at over 450 feet. The lake covers 120 acres.
The Cuyuna Range was discovered by Cuyler Adams, a surveyor who while exploring this area noticed an unnatural deviation in his compass needle. A compass needle is a magnet which will align itself to point to its “north”. Why? Because the earth is also a magnet. The inner of the earth is filled with a dense iron core which gives off a magnetic field. The compass needle detects the strongest pull and points to that direction (the North Pole). However, when a magnetic substance is detected closer to the compass, the compass needle will follow the closer magnetic substance (ie; iron ore).
After some research, Cuyler Adams discovered the reason the compass seemed to have a mind of its own; iron ore. Knowing that the Mesabi Range had been developed in northern Minnesota, Mr. Adams was sure that iron-bearing formations existed below the glacial overburden in this area.
Most iron ore deposits (pictured below) are found in chemical sedimentary rocks. Iron ore is a chemical sedimentary rock that forms when iron and oxygen (and sometimes other substances) combine in solution and deposit as a sediment. Hematite is the most common sedimentary iron ore mineral. Iron ore weighs pproximately 320 pounds per cubic foot. (A cubic foot is an area 1 foot x 1 foot x 1 foot)
Chert (pictured below) is a sedimentary rock material composed of silicon dioxide. It varies in color between white and black or between cream and brown. Grey, red and yellow are also commonly seen in chert. The dark color comes from inclusion of organic matter. Chert has been used in tool making in decades past. Chert weighs approximately 87 pounds per cubic foot.
Sandstone (pictured below) is a classic sedimentary rock made up mainly of sand-sized debris. It weighs approximately 155 pounds per cubic foot.
Slate (pictured below) is a fine-grained metamorphic rock that is an formed when shale or mudstone change thruogh metamorphism. Slate is composed mainly of clay materials and is used widely in roofing and flooring because of its appearance and durability. Slate weighs approximately 168 pounds per cubic foot.
To solve this Earthcache, answer the following questions.
Please email your answers to me when you log your find. Any logs where answers are posted will be deleted. Enjoy!
1. From the sign, what kind of mineral was extracted from this mine?
2. From the sign, what kind of minerals and rocks were left behind?
3. From the rock - examine the size of rock you see here and consider its makeup. With the information provided above, try your hand at some math and try to calculate its approximate weight.
4. Bonus: What historic event happened here on August 19, 1957?
Pictures of you at the site are appreciated, but not required to log this cache.
Sources: By permission through the Cuyuna Country: A People’s History book series, published by The Cuyuna Country Heritage Preservation Society and http://geology.com