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Jewelry, Gems, & Minerals/Found rocks that set off metal detector.



A friend of mine recently found a number of black rocks that set off his metal detector, and attract a magnet. These are varying in size and shape, and are mostly found in/near a stream in the woods. The rocks themselves are heavier than one would expect from their size. Any idea what he's found?

The specimen as indicated by picture 2 is most likely the mineral magnetite (Fe3O4), a very common mineral, often mined as an iron ore. It will attract a magnet and is very heavy. Picture number 1 looks more like a piece of slag. Any iron smelting facilities close to the point of discovery? Of course positive mineral identification is somewhat limited from pictures and descriptions. If you want to know more, you may want to consider our free mineral identification services from the Metropolitan State University of Denver as part of our community outreach. For details please see:  

Jewelry, Gems, & Minerals

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Uwe Richard Kackstaetter, Ph.D. (Dr.K)


I can answer questions concerning minerals, mineralogy, gems, metals, and anything that has to do with geology. However, I am NOT a jeweler. Questions about values, settings, gem stone cuts and appraisals are best directed to other experts on this site. I can however aide in the identification of unknown mineral materials. As a public service and part as training for new geoscientists, our university department provides FREE mineral identification for individuals. Please contact me for details or go to for details..


I am a professor of applied geology and mineralogy with many hours of field experience. Furthermore, I enjoy recreational gold prospecting and mineral collecting. As a professor I am engaged in research concerning minerals and their occurrence.

Member of the GPAA (Gold Prospectors Association of America) as well as the Association of Environmental Geochemists. Member of the GSA (Geologic Society of America) Member of the AIPG (American Institute of Professional Geologists)

Here is a small sampling: Mineral-rock handbook: Rapid-easy mineral-rock determination : written for anyone interested in minerals and rocks - Proctor, Peterson, and Kackstaetter;Macmillan Pub. Co. (New York and Toronto and New York) Physical Geology Laboratory e-Manual [CD-ROM], Kackstaetter, Earth Science Education LLC Colorado Front Range Self-guided Geology Field Trips, Kackstaetter,

Ph.D. in Applied Geology and Mineralogy. I am actively teaching courses in mineralogy and a variety of field courses with mineral collecting opportunities. Background in precious metal exploration.

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