Rocks on local roads attract his attention
Why is so much of the gravel used in Jackson County attracted to magnets? Is it chromite?
— Chris C., Jacksonville
Well, Chris, you get points for curiosity.
We took your question to several local and state agencies, but the most definitive answer came from Charles Lane, a professor of geology in the Department of Environmental Science and Policy at Southern Oregon University.
He explained that magnetite, chromite and pyrrhotite are three of the most common magnetic minerals and can be found in rocks in Josephine and, to a lesser extent, Jackson counties.
As placer minerals, magnetite (an iron oxide) and chromite (a chromium oxide) are more likely to settle in stream and river beds and appear in gravel and aggregate operations that utilize river gravel, such as those in the Applegate Valley, Lane said.
“Like gold, they are heavier than other minerals found in the stream or river, so they accumulate in certain areas since they are more difficult for the running water to move,” he explained in an email.
Aggregate material attained from a mountainside quarry, such as the one on upper Tolman Creek Road in Ashland, also could contain some pyrrhotite, an iron sulfide, Lane said.
Any of these minerals could be the reason for the magnetic pull you’re picking up on local roads.
Chris, if you’re still curious (and we know you are), the Oregon Department of Geology and Mineral Industries has an interactive page (www.oregongeology.org/sub/milo/index.htm) with information about the rocks and minerals found in specific mining operations statewide.
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