fossil?

July 2, 2024 11:40 PM

Is this a fossil? I picked it up on a beach.
posted by dhruva to Science & Nature (7 answers total)

Best answer: beach origin in particular makes the possibility that it is a sedimentary stone likely: "These rocks often start as sediments carried in rivers and deposited in lakes and oceans [usgs]." a Colorado School of Mines classification of sedimentary rocks includes various quartz compositions [U.Kansas]
posted by HearHere at 3:38 AM on July 3 [1 favorite]

Best answer: To me that looks like a nicely rounded pebble of pegmatite, which is a coarse-grained form of granite.
posted by heatherlogan at 5:41 AM on July 3 [2 favorites]

Can you give a bit more detail about where the beach was? That will help narrow it down an awful lot.
posted by sedimentary_deer at 9:56 AM on July 3

Response by poster: Bali, Indonesia
posted by dhruva at 10:02 AM on July 3

Best answer: I thought it might be a part of crinoid (radiating lines outward) but it's way too asymmetrical and lumpy. The processes by which something becomes a fossil seems to suggest that kind of aggregation is unlikely to be a fossil.
posted by spamandkimchi at 11:09 AM on July 3

Best answer: Thanks dhruva! My initial thought was that there were maybe some fossil corals in there - which would work with the general geology of Bali (that's just from a quick google. I'm a geologist, but I don't know anything about that area unfortunately). But ii looks like a conglomerate of some sort, with the dark parts and light parts have been smooshed together (technical term) - maybe with a volcanic origin. Neat rock though even if if there aren't any clear fossils in there!
posted by sedimentary_deer at 11:12 AM on July 3

Response by poster: Thanks all!
posted by dhruva at 10:17 AM on July 8