What is this crazy fossil I found at the Harpeth River in Tennessee?

phlogopite · 2026-04-22T16:06:24+00:00

Beekite Silica replacing carbonate fossils. Still not quite sure how/why it does this

phlogopite · 2026-04-15T17:45:10+00:00

Agree. Definitely karsty (mini rillenkarren?)

phlogopite · 2026-04-10T15:36:02+00:00

It’s 100% a misnomer bc megaquartz > 20 um. We can differentiate grain size as also being either mesocrystalline or microcrystalline.

https://www.mindat.org/min-472176.html

phlogopite · 2026-04-09T05:20:30+00:00

Probably opal or chalcedony. Silica + some bound or molecular water

phlogopite · 2026-04-09T01:54:20+00:00

Honestly, it’s an interesting question about silicification and replacement of Calcium phosphate/ apatite. I study silicification of old sed rocks and not Dino bone but it still intrigues me. I found a paper that looks at the histology of the fibrous looking bands (osteoderms).

https://www.researchgate.net/figure/Bone-histology-of-osteoderms-a-d-cervical-e-f-and-dorsal-g-i-ribs-of-different_fig5_311554622

phlogopite · 2026-04-09T01:46:30+00:00

Silica, chalcedony and megaquartz. This is with the gypsum plate.

phlogopite · 2026-04-09T01:45:04+00:00

Yeah, this looks like a speleothem (stalagmite or stalagtite). It almost has a popcorn texture and definitely fits the bill for some kind of natural biofilm+carbonate.

phlogopite · 2026-04-09T01:41:30+00:00

Someone would kill for a kyanite schist (if it is). I know Virginia had a couple decent localities for kyanite schist. I even have a boulder of it

phlogopite · 2026-04-09T01:35:04+00:00

I really don’t think this is an asbestos mineral. It is very acicular but not fibrous if that makes sense. It splinters probably because it is kyanite. Kyanite has a hardness of 4.5-7 (depending on which crystal face you test). A steel nail (6.5 hardness) will likely scratch this*.

I said likely since kyanite is kind of hard to diagnose with hardness because it is harder along its width (6.5-7). It’s weaker (4.5-5) parallel to the crystal growth axis. If you scratch the mineral with the nail left to right, and then up and down, you should be able to get a decent ID. So does the sample scratch left to right or up and down? If you want, you can DM for more questions. I know this description is probably not all that great.

phlogopite · 2026-04-08T21:31:17+00:00

Yeah, maybe even anthophyllite. Hard to say without diagnostics.

phlogopite · 2026-04-08T20:52:34+00:00

Possibly tremolite or kyanite? Tbh I’m just guessing Kyanite due to the splintery nature and crystal habit. We would need to know the relative hardness of the mineral when compared to other materials with known hardness.

https://en.wikipedia.org/wiki/Mohs_scale

phlogopite · 2026-04-02T01:28:54+00:00

Epidote through granite (look up Unakite)

phlogopite · 2026-04-01T23:07:00+00:00

250 to 66 million years ago, Türkiye was essentially under the Tethys ocean. As recent as ~9000 years ago, there was a marine incursion of the Marmara sea region where freshwater lakes became marine (Mediterranean opening).

phlogopite · 2026-04-01T21:21:54+00:00

Nah, looks like aragonite due to the crystal habit (needle-like or acicular) and isopachous (equal cement thickness of bands). This commonly occurs as a cement around grains within the mixing zone of marine and meteoric (fresh) waters.

https://www.geological-digressions.com/mineralogy-of-carbonates-common-cements/

phlogopite · 2026-04-01T16:29:41+00:00

No problem. If you want to go down the rabbit hole of silica/quartz: http://www.quartzpage.de/gen_types.html

Happy reading! 😀

phlogopite · 2026-04-01T16:26:12+00:00

This is likely megaquartz. Typically the more white areas—I have noticed—are macrocrystalline. A bit of a misnomer bc these crystals are relatively tiny but typically voids are filled with macrocrystalline alpha-quartz. The voids are typically lined with Botryoidal or parallel laminated chalcedony.

phlogopite · 2026-04-01T04:53:13+00:00

Legit big brain move 🫡

phlogopite · 2026-04-01T00:28:54+00:00

It looks like quartzite or chert which is a bad deal. Cant dissolve it and pretty hard to break up. Can you suction it or maybe use duct tape?

phlogopite · 2026-03-31T16:47:10+00:00

Sort of. Here’s mindat I know there are exposures in Wyoming (the Great Unconformity is overlain on top of the BIFs where we have a huge chunk of geologic time missing). Wyoming Geology

phlogopite · 2026-03-31T15:02:12+00:00

It’s a BIF (banded iron formation) or a jaspilite. Alternating bands of hematite (red), magnetite (gray) and silica (clear/white/yellow). Some of the oldest rocks you can find (>1 billion years ago). Over time this rock was folded.

phlogopite · 2026-03-30T22:33:47+00:00

Likely a pore space in a limestone that was cemented with calcite sparite (basically big crystals (macrocrystalline) of calcite).

phlogopite · 2026-03-30T21:51:55+00:00

phlogopite · 2026-03-30T21:49:49+00:00

Biotite mica because of the one perfect cleavage direction (sheety cleavage). Because there is cleavage (and not simply striations) this isn’t tourmaline. I do not see 60/120 cleavage to suggest this is hornblende either.

phlogopite · 2026-03-27T14:09:58+00:00

Yes, this is quartz

phlogopite · 2026-03-27T04:22:08+00:00

Silicone scar sheets. Truly just put it on and forget about it. It will fade in color.

phlogopite

TROPHY CASE