# What's up with this rock? **URL:** \ **Category:** Factual Questions\ **Created:** [October 30, 2019, 2:35am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682 "2019-10-30T02:35:37Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Omega\_Glory](https://avatars.discourse-cdn.com/v4/letter/o/7c8e57/32.png) [@Omega\_Glory](https://boards.straightdope.com/u/Omega_Glory)\ **Post date:** [October 30, 2019, 2:35am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/1 "2019-10-30T02:35:37Z")
Trypophobia sufferers beware. I’m wondering what could’ve made those pits, or if it’s a fossil. It was found in the Rochester NY area. [![Imgur](https://i.imgur.com/AgMLqJF.jpeg "imgur.com") ](https://imgur.com/AgMLqJF) ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [October 30, 2019, 2:43am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/2 "2019-10-30T02:43:56Z")
Couldn’t it be gases bubbling out of molten rock as it cooled down ? Like pumice ? ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [October 30, 2019, 2:44am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/3 "2019-10-30T02:44:24Z")
Yeah, it’s totally volcanic. ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [October 30, 2019, 3:24am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/4 "2019-10-30T03:24:11Z")
Looks like pumice. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 30, 2019, 3:30am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/5 "2019-10-30T03:30:15Z")
Out here in Cali those are very common. Might be a type of tafoni. > **[Tafoni](https://en.m.wikipedia.org/wiki/Tafoni)** > > Although various definitions can be found in the scientific literature, tafoni (singular: tafone) are commonly defined as small (less than 1 cm (0.39 in)) to large (greater than 1 meter (3.3 ft)) cavity features that develop in either natural or manmade, vertical to steeply sloping, exposures of granular rock (i.e., granite, sandstone) with smooth concave walls, and often round rims and openings. Recognized subcategories of tafoni include honeycomb, stonelace, alveolar (less than 2 cm (0.79 in)),... ETA: I didn’t read this blog but there are pics: > **[Pebbles with holes made by sea creatures](https://natureinfocus.blog/2011/04/09/pebbles-with-holes-made-by-sea-creatures/)** > >   Pebbles with holes in them are a common occurrence on the beaches along the Jurassic Coast in Dorset – and lots of other U.K. locations as well. Many of these tunnels, burrows or borings ha… ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 30, 2019, 3:45am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/6 "2019-10-30T03:45:05Z")
> [@Omega\_Glory](#): > > Trypophobia sufferers beware. I’m wondering what could’ve made those pits, or if it’s a fossil. It was found in the Rochester NY area. > > [Imgur: The magic of the Internet](https://imgur.com/AgMLqJF) What are the objects inside the holes? Was it found on the seashore? It looks to me like the [holes could be those made by piddock clams.](https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.redd.it%2Fk15ceqkgbt801.jpg&imgrefurl=https%3A%2F%2Fwww.reddit.com%2Fr%2Ftrypophobia%2Fcomments%2F7oxfze%2Fpiddock_clams_rock_boring_clams%2F&tbnid=X8qKDleA9Q12SM&vet=12ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ..i&docid=4E353luKP_l84M&w=2846&h=1536&q=piddock%20clam%20holes&ved=2ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ) ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 30, 2019, 5:18am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/7 "2019-10-30T05:18:08Z")
> [@Omega\_Glory](#): > > It was found in the Rochester NY area. > [@Colibri](#): > > Was it found on the seashore? I see you’re not on a seashore. However, the rocks of the Rochester area are entirely sedimentary, which pretty much rules out pumice if the rock is of local origin. ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [October 30, 2019, 6:10am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/8 "2019-10-30T06:10:14Z")
Could also be a fossilized sponge, couldn’t it ? ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 30, 2019, 6:19am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/9 "2019-10-30T06:19:23Z")
> [@Lucas\_Jackson](#): > > Out here in Cali those are very common. Might be a type of tafoni. > [Tafoni - Wikipedia](https://en.m.wikipedia.org/wiki/Tafoni) Not really, the holes are too unimodally-sized and widely spaced to be considered tafoni. The same factors rule against being pumice. > [@](#): > > ETA: I didn’t read this blog but there are pics: > > [Pebbles with holes made by sea creatures – Jessica's Nature Blog](https://natureinfocus.blog/2011/04/09/pebbles-with-holes-made-by-sea-creatures/) This would be my guess as well, looks like a sedimentary rock bored by bivalves to me. OP: There’s no indicator of scale on the picture, next time it would be a good idea to include one. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 30, 2019, 6:21am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/10 "2019-10-30T06:21:30Z")
> [@Kobal2](#): > > Could also be a fossilized sponge, couldn’t it ? Nope, doesn’t have enough openings and penetration of texture. ---
**Author:** ![Omega\_Glory](https://avatars.discourse-cdn.com/v4/letter/o/7c8e57/32.png) [@Omega\_Glory](https://boards.straightdope.com/u/Omega_Glory)\ **Post date:** [October 30, 2019, 3:33pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/11 "2019-10-30T15:33:24Z")
> [@Colibri](#): > > What are the objects inside the holes? Was it found on the seashore? It looks to me like the [holes could be those made by piddock clams.](https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.redd.it%2Fk15ceqkgbt801.jpg&imgrefurl=https%3A%2F%2Fwww.reddit.com%2Fr%2Ftrypophobia%2Fcomments%2F7oxfze%2Fpiddock_clams_rock_boring_clams%2F&tbnid=X8qKDleA9Q12SM&vet=12ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ..i&docid=4E353luKP_l84M&w=2846&h=1536&q=piddock%20clam%20holes&ved=2ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ) It looks like the things inside the holes are smaller rocks, but they’re too hard to see clearly. It does look like the rocks with the holes made by sea life. Here are some pictures with a CD for scale. [[Album] imgur.com ![](https://i.imgur.com/7Tt9BNS.jpeg?fb "imgur.com") ](https://imgur.com/a/NKiBKzm) ---
**Author:** ![tullsterx](https://avatars.discourse-cdn.com/v4/letter/t/e9bcb4/32.png) [@tullsterx](https://boards.straightdope.com/u/tullsterx)\ **Post date:** [October 30, 2019, 4:03pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/12 "2019-10-30T16:03:32Z")
[https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.redd.it%2Fk15ceqkgbt801.jpg&imgrefurl=https%3A%2F%2Fwww.reddit.com%2Fr%2Ftrypophobia%2Fcomments%2F7oxfze%2Fpiddock\_clams\_rock\_boring\_clams%2F&tbnid=X8qKDleA9Q12SM&vet=12ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ…i&docid=4E353luKP\_l84M&w=2846&h=1536&q=piddock%20clam%20holes&ved=2ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ](https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.redd.it%2Fk15ceqkgbt801.jpg&imgrefurl=https%3A%2F%2Fwww.reddit.com%2Fr%2Ftrypophobia%2Fcomments%2F7oxfze%2Fpiddock_clams_rock_boring_clams%2F&tbnid=X8qKDleA9Q12SM&vet=12ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ..i&docid=4E353luKP_l84M&w=2846&h=1536&q=piddock%20clam%20holes&ved=2ahUKEwie2IaniMPlAhVDOlMKHQhAC-AQMygFegUIARDXAQ) ---
**Author:** ![FluffyBob](https://avatars.discourse-cdn.com/v4/letter/f/ecb155/32.png) [@FluffyBob](https://boards.straightdope.com/u/FluffyBob)\ **Post date:** [October 30, 2019, 4:42pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/13 "2019-10-30T16:42:07Z")
Looks like plain old tufa to me. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 30, 2019, 7:58pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/14 "2019-10-30T19:58:36Z")
> [@FluffyBob](#): > > Looks like plain old tufa to me. Tufa isn’t unimodal in its cavity size. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [October 30, 2019, 8:19pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/15 "2019-10-30T20:19:29Z")
could have been inclusions of other minerals in the rock which eroded/dissolved away faster. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [October 30, 2019, 9:15pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/16 "2019-10-30T21:15:38Z")
> [@jz78817](#): > > could have been inclusions of other minerals in the rock which eroded/dissolved away faster. My guess as well. Mixed matrix stuff can have remarkable uniform bits when the settling out is about right. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 31, 2019, 4:56am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/17 "2019-10-31T04:56:20Z")
> [@jz78817](#): > > could have been inclusions of other minerals in the rock which eroded/dissolved away faster. \*Round \*minerals, though? And less resistant than whatever that finer matrix is? Exactly what rock are you proposing this originally was? It’s clearly not amygdaloidal basalt or andesite. It _looks_ very sedimentary, so you’re suggesting some sort of bimodal size distribution - in effect an _extremely_ will-sorted paraconglomerate where the clasts are both \*highly \*uniform and yet \*highly \*separated and much softer or more soluble than the matrix. I know of absolutely no rock that qualifies. The large clast fraction is usually the large clast fraction \*because \*it’s much more resistant. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 31, 2019, 11:54am UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/18 "2019-10-31T11:54:39Z")
> [@MrDibble](#): > > an _extremely_ will-sorted paraconglomerate That should be “[well-sorted](https://en.wikipedia.org/wiki/Sorting_(sediment)) paraconglomerate”. Or at least, well-sorted in the clast fraction. Being such a very bimodal distribution overall, the rock itself is very poorly sorted. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [October 31, 2019, 12:10pm UTC](https://boards.straightdope.com/t/whats-up-with-this-rock/842682/19 "2019-10-31T12:10:01Z")
Termites. Really really hungry termites.