Are there any geologists in here?

Are the stripes in the brownish part of the rock foliation? If so, then it's a metamorphic rock, right?

Where are all the geologists hiding? Help. Help! Is there a geologist in the room?

I think the paleofag is right. Could be part of a radioralite formation. The black part is chert, the brownish stuff in between silt- or sandstone? Dont think its metamorphic.

>Could be part of a radioralite formation.

How would you explain the shape? Almost looks like someone dipped some sandstone into liquid chert.

It's not "pretty" and not an artifact/fossil - so hit it with a hammer if you want a real answer.

How would that help?

If it is radioralite, the brown part is probably the "precursor" sedimentary rock that is was formed from, right? (Forgive my naive questions, geology is not my field).

If that is so, would it be feasible to detect remains of the radiolarians with a microscope? Or would the pressure and heat have homogenized everything? How would a geologist identify this rock?

In biology, we can key organisms based on morphology and other characteristics, isn't it possible to do the same with rocks?

Radiolarite is a marine sediment, the sandstone and chert layers have their origin in changing sedimentation conditions, so the sandstone is not the precursor. The piece you have is kinda rounded, i would say its has been transported by a river after diagenesis. Just guessing tho, although i study geology im more into geophysics.

I see. So how would you explain the clear boundary between the black chert and the sandstone? If the black parts are chert, wouldn't the entire rock be chert? After all, one must assume the entire rock was exposed to similar pressures and temperature, it's only 10 cm in size.

The clear boundary between Radiolarite and Sandstone is due to a sudden change in the sedimentation process. The Radiolarite part of the stone comes from the "background sedimentation" that always happens in the area it was sedimentated. If there is a storm or slumping underwater it leads to the sandstone, which is usually sedimented in higher areas than the radiolarite, to be transported further into the sea and it will sedimentate on top of the radiolarite. After this process has happened, the background sedimentation will continue which leads to alternating layers of sandstone and radiolarite. This could be how it happend, pic related is a similar case from one of my excursions to Elba, Italy.

Very interesting!

Could the roundness of the rock be due to grinding from the ocean, a river, or perhaps a glacier? If say a vertical fragment was washed out to sea for instance, ad then somehow ended up back on land?

Also, what is the hardness of chert? Is there any tests I could do at home that would strengthen the current hypothesis that it's sandstone and chert?

Chert is quartz so hardness is around seven.

Yes, the roundness could be from the transport in the river/ocean etc..

I would look for literature that desribes the geology of the place you found the stone. This could rule out/confirm the radiolarite guess. Its really hard to identify a stone this small just from a picture.

I checked the literature, and in my country there are three known places where chert is found, and where this rock was found is one of them. It was also found not far from the coast.

So am I correct in my understanding that chert can be composed of many different microscopic fossils, but Radiolarite is mainly composed of the microscopic remains of radiolarians?

If that is the case, how do geologists differentiate between them? Let's say I find a chert layer in the same place as this rock was found, how could I determine if it was radiolarite or not? I've seen some examples on line where the radiolarian fossils are visible. Is this usually the case?

It's been a very interesting thread, and thanks for all the information so far.

BTW, is there something like biological identification keys, but for geology? Surely by testing for hardness, ph, morphology, color, magnetism, microscopical clues, etc. one would be able to exclude possibilities and get closer to an identification of a rock sample?

lmao they put a fuckin handle on it holy shit

Turns out there are keys for rocks!

I'm gonna try to hammer off a piece of the black part and see if I get a conchoidal fracture. Then I'm gonna try to scratch some glass with it.

Throw it in an XRD then tell us the composition

I'm still waiting for the price and size of X-ray Crystallography Machines to drop..

$200 shoebox-sized when?

I'm taking physical geology. If anyone wants to do my mineral lab for me, feel free to do so.

This

maximum keks

I'm a geologist.

where did you find it?

did that last quarter. Now im doing structural.

Why is there so many geofags all the sudden?

Chert is not quartz dummy. Chert is silica and a by product of biomineralization.

let me explain

Chert is fossilized sediment from microorganisms called radiolaria in the oceans.

Chert is SiO2

And quartz is actually made plutonic and mid crustal conditions. It is SiO4, a continuous framework silicate.

Quartz and Chert do contain silica and oxygen, but they different structures all together and are formed from two completely different conditions.

BOO YAH, rockfag saves the day again..

that is an ASSAULT BULLET probably lost by some ancient SERIAL MASS MURDERER

Petrified Jew tail

But quartz is SiO2

Chert has the same chemical composition but with mild hydration and is formed via secondary crystallization of silicious minerals.

t. Chemist

Its basic building block is the SiO4 group, in which four oxygen atoms surround a central silicon atom to form a tetrahedron. Since each oxygen is member of two SiO4 groups, the formula of quartz is SiO2.

The SiO4 tetrahedra form a three-dimensional network and many mineralogy textbooks classify quartz as a network silicate or tectosilicate.

Eat it
Eat it
Eat it

chert is a form of microcrystalline quartz.
it's crystallographically different from other forms of silica, such as cristobalite or tridymite or stishovite or silica glass, but it's physically different from macrocrystalline quartz which makes those beautiful six-sided (but symmetrically trifold) crystals we know and love.
it's like the difference between calcite and micrite, which are themselves crystallographically different from aragonite.

t. that paleofag again

You could've just said chert is amorphous and we would understand.

>Geology thread on Veeky Forums
>its not flooded with /pol/ bullshit somehow

I love you geologists.

where's the fun in simple explanations?

I would. Could be fossils inside.

The romans were fucking awesome

Spotted the Jew.

>amorphous
>microcrystalline
pick one

to explain, since this is a /seriousdiscussion/ board, microcrystalline means that there are crystals, just that they're tiny and jumbled, so to the naked eye you can't see any. amorphous means that there is no crystal structure on any scale.
the difference between macrocrystalline, microcrystalline, and amorphous is more or less the difference between granite, rhyolite, and obsidian.

oy vey

>where did you find it?

Western coast of Norway.

Didn't see this topic. I actually though physical geology was going to be a cakewalk and it's not my focus but I have a question? If a mineral can be scratched by your finger nail, is it necessarily softer than your fingernail? Can it fall into harder than a penny but softer than glass category instead? I know it can it can be equal to the fingernail hardness. What would you choose considering I just had a question where a mineral was true that it could be scratched by a fingernail. I feel like it's a trap question.

Thanks for clearing that up.

question though,
What do you classify Opal to be?

I'm judging your answer btw.

they're amorphous but semi-ordered. there's some structure, but it doesn't repeat the way a true crystal does.

the only process of identifying microfossils is to have a good eye for them. Typically if you see and estimate a certain percentage of similar fossils across multiple samples from the same outcrop you can crudely attribute a further sedimentary name, like Radiolarite, to the rock instead of simply a chert. You just need a really good eye and alot of patience to be a sedimentologist. Geology identifiers are more interesting and more i suppose "relevant" for igneous or metamorphic rocks and minerals. Sediments can tell alot from basic induration, roundness, grain size etc as they're typically quartz and feldspar 90% of the time just in differing ratios. I would also like to guess very basically that your rock is from partially uplifted land thats been either eroded or cut by glacier and gained its smooth shape by travelling through a long glacial fluvial/fluvial track.

minerals is easy dude

You pass my mineral bro ;^)

It's a Skeksis claw.

Lmao

The building block is the SiO4 tetrahedra but the oxygen ends up getting shared by the silicon. The chemical formula for quartz is SiO2. did you even pass minerology

They're just called 'polymorphs'

>I need help identifying this weird rock.

It's a pyroclast, except that this is "man-made". It's waste product from processing whatever is being mined.

It's glass like appearance is due to vulcanisation whereby hot liquid rock such as ejecta from vulcanoes gets cooled very rapidly by landing in a river, lake etc. It's apearance is said to be vitrious and it's fracture is conchoidal. Should feel quite light for it's size.

Thats a claw

I know what the chemical formula is dip shit.

I'm talking about how it GEOMETRICALLY crystallizes. you dumb cuck.

No.

Chert is not a polymorph, reread polymorphism in your geochem book slacker.

So many dumb geologists on this site.

I really hope the geofags on here don't expect to
land an actual geology job.

Because, i'm not going to give you dumbfucks shit.

This.

and trips checked.

geology is for brainlets.