At my local beach, iron oxide leaks from the cliffs, and forms orange sand as it trickles onto the beach.
However, aside from around those trickles, the sand is black, as it is mostly (highest concentration in the world) fine dust of pure iron.
How does this happen?
What happens if you breathe the eyeurn dust?
u die.
Deoxidation of iron? What if its just a chromatic effect? More iron oxide builds until the orange hue becomes so dark it appears black?
The sand is magnetic.
>silicone is magnetic
More at 11
It's iron sand you dumb shit
Lower PH prefers deoxidation of iron. And silicates are easily oxidized (duh).
Or to expand on that, it's a net gain in stability if you compare the two half reactions side by side. It's not really odd if you consider that this is a fucking beach and there's water everywhere to allow reactions to take place.
Actually now that I think about it, +4 is already SiO2, so this explanation doesn't actually make any sense.
Must be some other pollution reacting with the iron.
I guess if the beach is super shitty and acidic, that would favor the H+ to latch onto the oxygen molecules of the iron oxide to form water.
The sand is unlikely to be pure iron. It's probably magnetite. Magnetite is already oxidised. Although it does react with oxygen to produce hematite (red rust like that coming from the cliffs), I'm not sure what the environmental conditions are to produce this or how quickly the reaction takes place.
Alternatively, the constant wave action on the beach could "polish" off any rust that has accrued while the tide is out (certainly the magnetite - hematite reaction would be slower under water).
Just a thought.
Polishing iron removes rust by subtracting it, not converting it.
i.e. by polishing rusty iron sand, you produce... rusty iron sand.
There's a rusty ship hull embedded in the sand, more evidence that it's not the waves.
And it does not appear to be magnetite, otherwise it wouldn't be orange to start with and would behave very oddly.
>silica is an oxide
>implying silica oxide
>And it does not appear to be magnetite, otherwise it wouldn't be orange to start with and would behave very oddly.
I thought you said the sand was black?
The sand is orange when deposited, but sand that is not recently deposited is black.
You said the orange sand is from iron oxide on the cliff.
Probably the sand is just being stained by whatever is leaching out of the cliff and the black sand was always there.
It's being actively deposited, but there's barely any of it: As I said, only recent deposits exist.
Well I don't know what to tell you without pictures.
Native iron is rare in nature because it oxidizes so quickly. It's more than likely just magnetite.
Note that magnetite can also be formed as rust, with water.
3 Fe + 4 H2O --> Fe3O4 + 4 H2
That equation describes oxidation, but either it starts out as iron oxide and deoxidises, or starts out as iron oxide and becomes magnetite.
>or starts out as iron oxide and becomes magnetite.
magnetite is iron oxide
The orange sand is not turning into black sand
The black sand is concentrated on the beach the same way it is concentrated by panning (such as for gold)
The orange sand runs off and the black sand is exposed at the same time (when it rains right)
The black sand is covered by lighter sand afterwards so the cycle can repeat
Even without reading the thread it should be obvious that is a silly explanation.
>silicone
Do you even know the difference between an oxide and oxidation?
An oxide by definition contains one or multiple oxygen atoms, so even though I never even said silicon oxide, "silicates" means the same fucking thing.
Oxidation refers to the formal charge of the central atom. Oxidizing an element means decreasing the electron density around that particular atom by bonding electronegative atoms to it, like oxygen, nitrogen, or any halogen, in order to pull electrons away.
Silicon atoms readily oxidize to form a plethora of different oxygen-containing silicates. A silicate is literally any silicon atom or atoms bonded to oxygen.
I was wrong in my initial assumption that there was any release in energy (gain in stability) in going from SiO2 to something like Si2O7 but it honestly doesn't matter compared to you; you're so far off you're not even wrong.
This is most likely an acid base reaction (assuming that it's true that iron is actually deoxidizing).
Its called Oxidation, not De-Oxidation
Maybe the sand has been stained by tar or oil. Was there an oil spill nearby?
why would the iron be De-oxidizing? Are you heating it? Are you melting it? Are you blasting it with coke and flux?
(4)H+ + FeO2 --> Fe + (2)H2O
Pouring acid on it I guess.
Don't think heat is required for this reaction considering how easily H2O is formed.
Neat. My hail marry guess is that the Iron (III) is being reduced by bacteria to Iron (II), which is black.
There's something called the Electron Transport Chain which is essentially how an organism creates energy (ATP). Typically, oxygen is the final acceptor and is reduced to water, but there are other electron acceptors that have been adapted by microbiota. It's been a long time since I've studied bacteriology, or even biology, so take that explanation with a grain of salt.
Another explanation that might be more likely is that over time, the red oxide is slowly washed down into the sand and diffuses to the point where its optical properties are diminished and its no longer noticeable.
OP every single person who posted in this thread so far doesn't know what the fuck they are talking about
You're going to have to give us more information about the composition of the cliffs. Could you try to provide a better description of the cliffs?
Where is this beach?
>fine dust of pure iron.
doesn't happen in nature
>every single person
and every married person
This. I want to see pics.
Patea beach.
The fairly-orange cliffs were formed volcanically, and they erode at a considerable pace.
While a lot of anons seem to insist that the erosion is not adding to the iron, and instead diluting it, I don't think fast-paced dilution would allow it to have the richest ironsand in the world.
fuck you Im married and I know what Im talking about
prob magnesium dust
The person that guy originally responded to did not post this.
Okay OP I have your answer.
The article I've linked below indicates that the most recent volcanic succession in your area is andesitic in composition. Actual composition could vary locally thus the cliffs you speak of may not be strictly andesitic, but likely close enough for the purpose of this analysis. These andesites contain iron-bearing minerals such as pyroxenes and magnetite. There may also be olivine and amphibole present in the sands, perhaps even in the cliffs themselves as well.
The iron in these minerals is in its reduced form. Conditions at the Earth's surface are currently oxidizing. When the cliffs are exposed and chemically weathered the iron in these minerals becomes oxidized, forming an iron oxide that is orange in colour. This process is somewhat similar to the way rust forms on the body of a car. To be continued in next post
The chemical weathering of these cliffs occurs more slowly than their physical breakdown to detrital minerals. These black minerals, containing iron still in its reduced form, are remobilized and deposited to form a beach placer. Through a variety of sedimentological mechanisms, the densest minerals are separated and deposited to form a placer deposit (in this case a beach placer). The densest mineral here is magnetite which is quite rich in iron, forming your rich ironsand.
It is likely that the succession forming your cliffs is being physically eroded very rapidly elsewhere along the coastline and the magnetite is being brought to your beach by longshore currents.
The exact mechanisms by which the magnetite is concentrated are complicated and probably beyond the scope of this explanation. You might find the article I've provided to be of interest.
I said this already
The oxidised iron actually comes from pores in the rock, it's not exposed iron that then oxidises.
I don't have and can't find any pictures of a leaking cliff, but it's bright orange, so I'd say that any amounts of black minerals are negligible.
It's unlikely that this process is not somehow turning orange minerals black, because no black minerals come out of the cliffs, yet there are no orange minerals on the beach except where new sand is being added.
Ok
The oxidized iron comes from groundwater percolating through the cliff and oxidizing the minerals there. When it rains it washes out of the cliff and onto the beach.
The black minerals on the beach are an unrelated placer deposit of magnetite. The black and orange minerals are not part of the same system. They just happen to be in the same place.
Very fine? Check. Colorless? Check. You answered your own question: iron particles de-ionized, or without charge. That's not to say that they won't have charge, but that the charge they had as non-oxidized solid iron, that charge has been removed, destroying its complex bonding potential. Exposure to air will revitalize its charge in dust form tho.
Hi I'm the guy that posted the articles above
You're correct about the groundwater moving through the cliff
However the other things you said are not true. The placer deposit is not unrelated; it is derived from the same succession as the cliffs.
Geology and Geophysics faggot here.
My first assumption was that it was the chemical weathering of pyrite in the cliffs.
2FeS2(s) (Pyrite) + 7O2(g) + 2H2O(l) = 2Fe2+(aq) + 4SO42−(aq) + 4H+(aq)
4Fe2+(aq) + O2(g) + 4H+(aq) = 4Fe3+(aq) + 2H2O(l)
Fe3+ has a naturally orange - red coloration to it.
You can see orange runny rusty shit in concrete all of the time, it's caused by pyrite weathering.
Then op told us the beach, which they should've done in the first post. I did some digging. I found a picture of the beach and recognized that the rock around the beach looks very basaltic. Magnetite now makes since, because pyroxenes olivine, and amphibole make up basalt. I found a particular paper on the composition of the sand. Pic very related. I imagine that the basaltic rock mechanically weathered through the tidal action of the ocean water. The constant supply of water moving back and forth may somehow influence the chemical weathering of mineral fragments that had / have weathered mechanically. The Fe 2+ and 3+ content is from the minerals. The olivine and amphibole in the rock must have a high content of Iron, rather than magnesium.
As far as why does the sand keep turning different colors? I think it's just the constant oxidation and reduction of hematite and magnetite due to the cyclic nature of tides. Hematite ( iron(III) oxide ) giving it an orange color, and magnetite ( 2 iron (III) 1 iron (II) oxide ) giving it an orange and black color as well.
I don't really know if there's a 100% true answer to this though. I know that Veeky Forums likes the absolute truth, but there really isn't absolute truth in geology.
This video is really appropriate for this thread though: youtube.com
It's clear that some of you faggots don't give a shit about rocks.
Fellow Geologist here in concurence with this chaps explanation. I should like to point something out to OP and perhaps some other fellows in this thread that has been overlooked: the nature of any typical [non-deltaic] shoreline is dominated by sediment transport, usually by processes of Long-shore currents, rip-currents and tidal currents (amongst other possible currents).
With this in mind, it may be worth considering the transport which the 'Orange Sediment' is forced to undergo. That is to say, the [presumed] Heamatite proximal to the cliff face is periodically exposed to and transported by incoming seawater, thus removing it from the backshore/foreshore environment.
This periodic transport may explain why the Heamatite is only found proximal to the cliffs.
It would be audacious to suggest that the Heamatite is not chemically altered during its exposure to seawtaer, however; seawater is a very strong geochemical fluid and would almost certainly have an affect on any heamatite present.
You morons are a fucking disgrace to the profession
I sincerely hope you're just students
Wow
Please never practice geoscience
If you do practice geoscience you are a danger to the public. If you hold any professional credential then you should rescind it immediately.
Samefagging is real
Yes I made both of those posts.
What the fuck are you talking about?
I want to marry and impregnate repeatedly a tigergirl.