Jollyfritos123 Posted November 24, 2022 Share Posted November 24, 2022 Can someone please help me identify this rock I found today in Morgan hill CA. It is definitely the most interesting looking rock I’ve found. Any input is appreciated! Link to comment Share on other sites More sharing options...
jasong Posted November 24, 2022 Share Posted November 24, 2022 Not an easy one to ID there. Being wet (and oxidized outside?) isn't helping either. I don't know what this one is. I'd lean towards some ultramafic igneous rock like peridotite or pyroxenite. Could be some metamorphism happening there too making it harder, or something like an igneous intrusion in metamorphics. The crystals being either peridot or diopside, respectively if peridote or pyroxenite. But the color is kinda off for both of those, so dunno. Beryl can be that color, but it doesn't seem like a hostrock for beryl, so... A scratch test on the crystals might help narrow things down. So would the local geology. But that looks like one that easier to ID in hand with magnifier loupe than via picture. So unless anyone else recognizes it as a local rock, might be one to take to a geologist to ID. 2 Link to comment Share on other sites More sharing options...
GeoBill Posted November 27, 2022 Share Posted November 27, 2022 Hard to tell from the picture. The surface looks polished or 'slickenside' like what you might find in a fault zone. There also appears what might be a somewhat flattened orientation in the broken surface in the first picture. I have some similar looking samples that were boudins in serpentinized ultramafic dikes in Franciscan fm which is most likely the local rocks in your area. Link to comment Share on other sites More sharing options...
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