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Identity HelpCalcite ID in stones in Santa Rosa CA creek
26th Mar 2024 23:57 UTCPaul Hernday
I'm finding that my hunch is pretty good at visually distinguishing calcite from quartzite prior to the acid test, but I'm not sure why. Maybe it's the context of the type or shape of rock, or the flatter white of the calcite or ??? Any signs others have noticed?
Questions Answered
Can it scratch glass? : No
Can you scratch it with your fingernail? : No
Is it light/heavy for the size? : Normal
27th Mar 2024 01:20 UTCJohn Christian
27th Mar 2024 03:12 UTCPaul Hernday
27th Mar 2024 05:21 UTCHenry Raab
27th Mar 2024 06:06 UTCJohn Christian
Newer rocks were fractured by the earthquakes caused by the plate motion and then filled with calcite.
See if the calcite veins are fluorescent.
27th Mar 2024 13:57 UTCEd Clopton 🌟 Expert
29th Mar 2024 14:38 UTCGregg Little 🌟
Ed Clopton 🌟 Expert ✉️
mineral quartz that started out as sandstone, which in turn started out as quartz sand. Ed; I couldn't resist going further down your technical rabbit hole so do forgive me. The word "sandstone" in this case should be replaced with "quartz arenite". The term sandstone is actually a detrital rock grain-size term (1/16 to 2 mm) where the clasts could be any mineral or lithic fragment. Virtually everyone assumes it is mineralogically a quartz sand which is usually accurate, sort of by default as quartz being highly resistant usually is the last mineral standing in the erosional processes.
29th Mar 2024 15:52 UTCEd Clopton 🌟 Expert
Arenite must derive from the Latin arena for sand, so arenite = sand+stone. Cool! So "quartz sandstone" wasn't far off!
30th Mar 2024 03:47 UTCGregg Little 🌟
Cheers, Gregg
27th Mar 2024 15:41 UTCKyle Beucke 🌟
The rock on the lower-right may be "greenstone," i.e., seafloor basalt that was hydrothermally altered (while it was still on the seafloor?).
Breaking some of these open would help in a rock ID as well as seeing the vein textures more clearly (e.g., avoiding effects of surface weathering).
Kyle
27th Mar 2024 17:12 UTCPaul Hernday
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