In the article by British red, he states that flint is derived from sponges!! Unless I missed a trick in Geology, could he clarify this statement? Good article otherwise! 
Flint from sponges?
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andyn
Bushcrafter (boy, I've got a lot to say!)
I'm sure BR can give you a definitive answer, because i'm not sure which article your refering too, but I think the early stages of what make up flint was formed from the silica from disolved dead sea sponges.
So not only do you clean your car with them...but you can make arrow heads from the too
Ok i'm sure there a million odd year process involved in there too somewhere.
So not only do you clean your car with them...but you can make arrow heads from the too
Ok i'm sure there a million odd year process involved in there too somewhere.
Sure mate - "from sponges" is an over simplification, but, most of the silica that makes up the flint nodules is biogenic. Although flint itself is an inorganic mineral, most of the silica derives from the internal skeletons of sponges in the form of spicules , which were common in the marine environment at that time.
The silica from these sponges dissolved and formed a fluid 'gel', contemporaneously with the deposition of the chalk. Pre-lithified chalk is a calcareous ooze on the sea floor, so this gel, a 'mobile, gelatinous, silica-based mass', flowed through it and was thus redistributed. Eventually, it accreted around nuclei of marine detritus, which could have been the remains of other sponges. As the gel stopped flowing, it dehydrated and hardened into the microscopic quartz crystals which constitute flint.
Makes nice arrow heads too
Red
The silica from these sponges dissolved and formed a fluid 'gel', contemporaneously with the deposition of the chalk. Pre-lithified chalk is a calcareous ooze on the sea floor, so this gel, a 'mobile, gelatinous, silica-based mass', flowed through it and was thus redistributed. Eventually, it accreted around nuclei of marine detritus, which could have been the remains of other sponges. As the gel stopped flowing, it dehydrated and hardened into the microscopic quartz crystals which constitute flint.
Makes nice arrow heads too
Red
Not mine mate 
I should have credited it...most remiss of me in fact...bad Red...
http://www.bbm.me.uk/portsdown/PH_320_Flint.htm
Red
I should have credited it...most remiss of me in fact...bad Red...http://www.bbm.me.uk/portsdown/PH_320_Flint.htm
Red
British Red said:Sure mate - "from sponges" is an over simplification, but, most of the silica that makes up the flint nodules is biogenic. Although flint itself is an inorganic mineral, most of the silica derives from the internal skeletons of sponges in the form of spicules , which were common in the marine environment at that time.
The silica from these sponges dissolved and formed a fluid 'gel', contemporaneously with the deposition of the chalk. Pre-lithified chalk is a calcareous ooze on the sea floor, so this gel, a 'mobile, gelatinous, silica-based mass', flowed through it and was thus redistributed. Eventually, it accreted around nuclei of marine detritus, which could have been the remains of other sponges. As the gel stopped flowing, it dehydrated and hardened into the microscopic quartz crystals which constitute flint.
Makes nice arrow heads too
Red
Where was you when I was doing Geology! Cheers Red! :You_Rock_
British Red said:Sure mate - "from sponges" is an over simplification, but, most of the silica that makes up the flint nodules is biogenic. Although flint itself is an inorganic mineral, most of the silica derives from the internal skeletons of sponges in the form of spicules , which were common in the marine environment at that time.
The silica from these sponges dissolved and formed a fluid 'gel', contemporaneously with the deposition of the chalk. Pre-lithified chalk is a calcareous ooze on the sea floor, so this gel, a 'mobile, gelatinous, silica-based mass', flowed through it and was thus redistributed. Eventually, it accreted around nuclei of marine detritus, which could have been the remains of other sponges. As the gel stopped flowing, it dehydrated and hardened into the microscopic quartz crystals which constitute flint.
Makes nice arrow heads too
Red
And I guess this is in simple Laymans terms, as I sit here scratching my head with a confused expression on my face!!
Way to intelligent for my two brain cells to comprehend!
But sponges wont work with your traditional steel,you'll still need flint.British Red said:"Flint is made from sponges"
Greg said:
What do you mean, us computer geeks only need one brain cell! Which is a good thing as I would not like to say how many brain cells I have killed over the years with the booze
Great explanation Red.
Ok, So I just spent a very cold and wet night. I couldn't get a fire gping for love nor money. the blooming sponge just wouldn't throw a spark from the fire steel, no matter how hard I tried, and you won't believe the mess the flint made of the car's paintwork. Is it Me?
xylaria
Bushcrafter (boy, I've got a lot to say!)
Is the pre lithified chalk the reason why there is that hard white stuff on the outside of the flint nodule?
Hi
I do not want to be a party-pooper but the idea of a gelantinous mass, oozing around in the calcareous mud is a bit out of date.
The silica (yes, from sponges i.e. biogenic) was dissolved in seawater, just as it is today. This was also in the chalk mud and could percolate down through it. Beyond about 7m below the surface of the mud, oxygen could no longer reach, and anoxic bacteria lived and were gobbling up organic matter. This (their waste products) created an acidic environment.
The acid (H2SO4) dissolved the chalk mud but silica also precipitates in an acidic environment, so as one dissolved, the other precipitated. This contemporaneous precipitation can be established by trace minerals - in the flint and surrounding chalk - as they are nearly the same. They are in slightly lower concentrations in the flint which shows that the chalk was further compacted slightly after the flint formed but they are essentially the same.
This replacement of one whilst the other dissolved explains the excellent preservation of such things as the burrows of Thallasinoides. The organic matter was often concentrated in old burrows and therefore formation started there; 'finger flints' are often casts of these burrows.
The old theories - several of them - gel flowing, gel 'pooling' in dips in the mud surface - do not explain all the known facts about flint - e.g. the contemporaneous formation and mineral concentrations.
Why is flint in 'layers' - visible in any chalk cliff - something to do with the Milankovich cycles - these are all to do with the variations in the Earth's orbit but exactly how they triggered it, I have never researched (even if the answer is known).
Hope that is all clear. Tests will be held later
I do not want to be a party-pooper but the idea of a gelantinous mass, oozing around in the calcareous mud is a bit out of date.
The silica (yes, from sponges i.e. biogenic) was dissolved in seawater, just as it is today. This was also in the chalk mud and could percolate down through it. Beyond about 7m below the surface of the mud, oxygen could no longer reach, and anoxic bacteria lived and were gobbling up organic matter. This (their waste products) created an acidic environment.
The acid (H2SO4) dissolved the chalk mud but silica also precipitates in an acidic environment, so as one dissolved, the other precipitated. This contemporaneous precipitation can be established by trace minerals - in the flint and surrounding chalk - as they are nearly the same. They are in slightly lower concentrations in the flint which shows that the chalk was further compacted slightly after the flint formed but they are essentially the same.
This replacement of one whilst the other dissolved explains the excellent preservation of such things as the burrows of Thallasinoides. The organic matter was often concentrated in old burrows and therefore formation started there; 'finger flints' are often casts of these burrows.
The old theories - several of them - gel flowing, gel 'pooling' in dips in the mud surface - do not explain all the known facts about flint - e.g. the contemporaneous formation and mineral concentrations.
Why is flint in 'layers' - visible in any chalk cliff - something to do with the Milankovich cycles - these are all to do with the variations in the Earth's orbit but exactly how they triggered it, I have never researched (even if the answer is known).
Hope that is all clear. Tests will be held later
xylaria said:
I forgot to say. The cortex on the outside of nodules - it is not certain yet whether this is a feature relating to formation or breakdown of the flint.
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