Palisades Sill NJ

[Photon]

The Palisades Sill in NJ is an extrusive volcanic formation. The rocks are said to be Diabase which is similar to Basalt. The rocks are beige inside but have a dark oxide/weathered looking skin. Anyone know what the beige material is? And what is the dark skin?

 

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[Tony in SC]

Does the dark area face north?

 

[ToddsPoint]

Igneous rocks are divided into two types, based on silica content. Lighter colored rocks, like you pictured are called felsic, with high silicon content. Diabase and basalt are mafic rocks with less silica and are darker in color. Don't know the exact type you posted but would say it's likely not diabase from my experience. Gary

 

[Photon]

No it faces East

 

[Photon]

Yes that sounds reasonable and I’ve thought about it too except that all the literature that I find call it a diabase! Could diabase be light colored?

 

[ANTIQUARIAN]

Maybe consider re-posting your question here as well... Geological Forums

Welcome to Tnet from Toronto!
Dave

 

[ToddsPoint]

Yes that sounds reasonable and I’ve thought about it too except that all the literature that I find call it a diabase! Could diabase be light colored?

Maybe weathering makes it light colored? Diabase should be dark under the patina. Gary