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Identity Helpfound in The Netherlands

24th Apr 2024 14:16 UTCAlexander Turksma

I have found this almost 10 kilo rock in an area of glacial deposits in the Netherlands. But have no clue what it is? Hope someone knows.

Questions Answered
Can it scratch glass? : Yes
Can you scratch it with your fingernail? : No
Is it light/heavy for the size? : Heavy

24th Apr 2024 14:44 UTCAlexander Turksma

closeup

24th Apr 2024 15:18 UTCHarold Moritz 🌟 Expert

Probably some kind of quartz/chalcedony. I found stuff like this in similar deposits in northern Germany.

27th Apr 2024 08:43 UTCAlexander Turksma

after closer inspection it contains micro fossils and has fossil structures.

24th Apr 2024 15:53 UTCWayne Corwin

Looks like a silicified coral. Does it have small pockets of quartz crystals? I can't tell from the photos for sure, but it looks like many, many small holes with branching structure around them?

More close ups would help.

24th Apr 2024 17:17 UTCAlexander Turksma

here a closeup, but your description is about right i think but the rock is layered all around

24th Apr 2024 22:40 UTCWayne Corwin

Is the rock wet in your photos?

It should be dry.

25th Apr 2024 08:39 UTCAlexander Turksma

when it dry you don't see anything, but here a photo of the dry stone. it is also a ventifact

25th Apr 2024 09:00 UTCRalph S Bottrill 🌟 Manager

It looks like a shaped artefact - an axe head? Rather worn.

Other than that it looks like a silicified limestone rich in coral and shells.

25th Apr 2024 11:15 UTCWayne Corwin

A 10 kilo axe head Ralph???

25th Apr 2024 13:53 UTCAlexander Turksma

it measures 27 x 18 x 10 cm so defently no axe head

25th Apr 2024 09:44 UTCHans-Jürgen Haas

Can it scratch glass? : Yes

Hello.....

does every part of the stone scratch glass or only parts of it?

According to the picture I would guess it is fluorite with baryte and quartz, unrolled by a river or maybe glacier....

25th Apr 2024 13:54 UTCAlexander Turksma

it is made completely of quartz and quartz related minerals like chalcedony and some jasper and agate bands. Here is a photo of the side which shows banding that go's all around the rock.

27th Apr 2024 08:40 UTCAlexander Turksma

the hole stone can not be scratched by a knife so harder the glass.

26th Apr 2024 01:24 UTCGregg Little 🌟

The rock has the textures of a very fossiliferous higher energy deposit similar to coquina; note abundant porosity. The silicification preserved the fossil texture very well. Besides possible coral and shelly material, other fossils appear to be gastropods with the fossil debris coated and bound by calcite, now silicified, from probable bacterial and algal activity. The layers also indicate bedding possibly from wave reworking in a nearshore environment.

26th Apr 2024 08:55 UTCAlexander Turksma

it contains no fossils at all, all quartz

27th Apr 2024 02:21 UTCGregg Little 🌟

Alexander Turksma ✉️

no fossils at all, all quartz

Quartz is a mineral and fossils are animal and plant remains or sometimes no plant or animal at all, as in the case of trace fossils (i.e. foot prints, coprolites, burrows, etc.). They are not mutually exclusive either as some fossils grow siliceous skeletons and other fossils can be replaced by quartz (pseudomorphs).

In fact your rock is full of fossils, apparently silicified (turned to quartz) as you state "the rock scratches glass". If you look closely at the individual fragments you will see geometric forms; crescents, chambers, radial, circular, etc. the tell tail signs of fossils.

27th Apr 2024 08:37 UTCAlexander Turksma

my apologies, your where right i have taken a second closer look at the stone with a 10x Loep and indeed see fossil like structures. Could this be a stromatolite type stone?

27th Apr 2024 05:19 UTCStefan M.

Im looking at this, im not at all convinced this is jasper and chalcedony- they are pitted, not porous. Pretty sure this is some form of calcite...are you absolutely certain that it scratches glass? Did you try scratching it with a steel object?

27th Apr 2024 08:37 UTCAlexander Turksma

a steel knife does not scratch it.

27th Apr 2024 07:43 UTCFranz Bernhard Expert

Nobody is jumping on Harold´s and Hans-Jürgen´s suggestions?

River-tumbled piece of a silicified baryte vein?

27th Apr 2024 20:50 UTCAlexander Turksma

i finally know what my rock is, it is a zoned silification rock from the eastern gravel in the netherlands Elbe and Wezer

27th Apr 2024 22:14 UTCRalph S Bottrill 🌟 Manager

So it’s a silicified shell deposit, could be labelled silcrete and the rocktype and location could be added to Mindat.

1st May 2024 15:13 UTCGregg Little 🌟

Alexander Turksma ✉️

zoned silification rock

This is not a good technical name for a rock. "Zoned" is a textural or genetic term and silicification is term for alteration; metasomatic, permineralization, etc.

1st May 2024 15:14 UTCGregg Little 🌟

Ralph S Bottrill 🌟 Manager ✉️

silicified shell deposit

Thanks Ralph.

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