Where is Iridescent Goethite found?
Goethite (α-FeOOH)
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Open the appIridescent Goethite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Iridescent Goethite
Michigan, USA
The Upper Peninsula of Michigan, particularly the Iron Ranges, is known for producing excellent specimens of iridescent goethite, often associated with hematite and other iron ores.
Germany
Various localities in Germany, especially in the Siegerland district, have yielded fine iridescent goethite specimens.
England
Cumbria and Cornwall are historical mining regions where goethite, including iridescent varieties, can be found.
Brazil
Some iron ore deposits in Brazil have produced iridescent goethite, often in botryoidal forms.
Collecting tips
- Look in Iron-Rich Environments. Focus your search on areas known for iron ore deposits, gossans (weathered cap of an ore body), and areas with significant weathering of iron-bearing rocks.
- Examine Cavities and Vugs. Iridescent goethite often forms as coatings or botryoidal growths within open spaces in rocks, so inspect vugs and fractures carefully.
- Check for Weathered Surfaces. Since goethite is a weathering product, look for specimens on weathered rock surfaces or in soil overlying iron-rich bedrock.
- Observe Luster and Color Play. The most distinctive feature is the iridescent, metallic sheen. Rotate specimens under light to observe the full spectrum of colors.
Quick Check
- Color:
- Dark brown to black with iridescent blue, green, gold, purple, red surface colors.
- Luster:
- Submetallic to metallic, with strong iridescence.
- Streak:
- Yellowish-brown to brownish-yellow.
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