Where is Shale with Iron Staining found?
Shale (sedimentary rock) with iron oxides
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Open the appShale with Iron Staining 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 Shale with Iron Staining
Appalachian Basin, USA
Extensive shale formations (e.g., Marcellus Shale, Utica Shale) often exhibit iron staining, particularly in outcrop exposures or near fault zones where fluids have migrated.
Western Canada Sedimentary Basin
Various shale units, including those associated with hydrocarbon plays, can show evidence of iron oxidation, especially in weathered zones.
North Sea Basin, Europe
Shale sequences within this prolific hydrocarbon basin can display iron staining, particularly in shallower sections or where exposed to meteoric water.
Anywhere shale outcrops are exposed to weathering
Iron staining is a common weathering product on shale surfaces globally, as iron-bearing minerals within the rock oxidize upon exposure to atmospheric oxygen and water.
Collecting tips
- Look for Fissility. Shale's most distinctive feature is its tendency to split into thin layers. Look for this characteristic in road cuts, stream banks, and outcrops.
- Observe Color Variations. The reddish, yellowish, or brownish hues indicative of iron staining will be superimposed on the typical gray, black, or green colors of fresh shale. Look for these color changes, which can be uniform or patchy.
- Check for Softness. Shale is relatively soft and can often be scratched with a knife. The iron staining does not significantly alter its hardness.
- Examine Weathered Surfaces. Iron staining is often more pronounced on weathered surfaces where oxidation has had more time to occur. Look for rusty-colored coatings or bands.
Quick Check
- Color:
- Dark gray, black, green, or brown with reddish-brown, yellowish-brown, or orange-brown staining.
- Luster:
- Dull to earthy.
- Streak:
- White to light gray for the shale matrix; iron-stained areas may produce a reddish-brown or yellowish-brown streak if the iron oxides are abundant and soft enough to leave a mark.
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