White patina on rocks! Chert?

[Artfuldodger]

I found a dug pile of clay/dirt near me. Lots of quarts and iron related rocks. I sometimes look through it after a heavy rain. Anyway, I found a few rocks that have this white layer or patina. I've read about arrowheads having this as well as chert rocks and flint. Here is a couple from that pile.
One looks like blue and gray layers/bands with some red spots of iron. The other one has more of the white stuff. From what I gather, it's not a coating but the actual rock breaking down from acid in the air and soil.

Do they look like chert? Here is the first one. It's sorta translucent. Hard to tell with all that white stuff on it.

 

[Nicodemus]

Hard to say. That looks like it might be chalcedony.

 

[Artfuldodger]

OK, here is the one that has layers. It's even more translucent. Kinda blue & gray.

 

[Artfuldodger]

Hard to say. That looks like it might be chalcedony.

I was thinking that it might be that as well. I'm just learning about chert, flint, chalcedony,jasper, and agate as well. They all seem kinda related.
There is a rock dig at Graves Mountain soon with lots of vendors and rock club members. I may take them with me to show those folks.

 

[NCHillbilly]

Looks like metaquartzite to me. Lots of it around here.

 

[Nicodemus]

I was thinking that it might be that as well. I'm just learning about chert, flint, chalcedony,jasper, and agate as well. They all seem kinda related.
There is a rock dig at Graves Mountain soon with lots of vendors and rock club members. I may take them with me to show those folks.

All those you mentioned break with a conchoidal fracture, so they can be knapped.

The only place on the North American continent you will find true flint is at Georgetown Texas.

 

[Artfuldodger]

Last one has that white patina and may be just quartz. There are a lot of round polished quartz rocks in this pile that look frosted. I find them in my yard as well. I read that there was probably a river here millions of years ago. That's why you can find river rocks in your yard.

This rock isn't very translucent looking. Flashlight doesn't shine through it like it does in most quartz. That's why I'm not sure it is quartz. The polished quartz rocks in this pile just look frosted with maybe some white patina.

This one though looked different from them. The white stuff looks deeper into the rock. I think it would be translucent if it wasn't frosted by nature.

 

[NCHillbilly]

Last one has that white patina and may be just quartz. There are a lot of round polished quartz rocks in this pile that look frosted. I find them in my yard as well. I read that there was probably a river here millions of years ago. That's why you can find river rocks in your yard.

This rock isn't very translucent looking. Flashlight doesn't shine through it like it does in most quartz. That's why I'm not sure it is quartz. The polished quartz rocks in this pile just look frosted with maybe some white patina.

This one though looked different form them. The white stuff looks deeper into the rock. I think it would be translucent if it wasn't frosted by nature.

Not quartz, it's quartzite. Big difference. The creeks and rivers and ground are full of it around here, looks just like that. The foundation of my mom's house and here rock retaining wall are made of it. Comes in all colors-white, yellow, orange, red, brown, blue/gray, sometimes banded. I've knapped a lot of it over the years, and many of the points I find here are made from it. It's very tough stuff.

 

[Artfuldodger]

All those you mentioned break with a conchoidal fracture, so they can be knapped.

The only place on the North American continent you will find true flint is at Georgetown Texas.

I read that a lot of what people call flint, isn't really flint. Same as agates. I did see some of those Georgetown points as well as a flint rough with the white patina. That flint looks blue/gray.

Was also reading where people fake the patina on points. Saw some pictures and even to me they looked really fake.

 

[Artfuldodger]

Not quartz, it's quartzite. Big difference. The creeks and rivers and ground are full of it around here, looks just like that. The foundation of my mom's house and here rock retaining wall are made of it. Comes in all colors-white, yellow, orange, red, brown, blue/gray, sometimes banded. I've knapped a lot of it over the years, and many of the points I find here are made from it. It's very tough stuff.

OK, thanks. I didn't think that one was chert or flint. It just looked different but not quite like quartz. Those first two look different from metaquartzite. They don't look grainy at all.

After looking at pics of metaquartzite and quartzite there is some of that in this pile as well.

There is also lots of slate in this area and in this pile.

 

[NCHillbilly]

All those you mentioned break with a conchoidal fracture, so they can be knapped.

The only place on the North American continent you will find true flint is at Georgetown Texas.

This quartzite is knappable, but you have to work it with a big wooden billet and hit it like you're trying to kill a snake. Every Savannah River point you find here is made of it, plus a lot of other point types.

 

[Artfuldodger]

Chalcedony and chert are varieties quartz with a fine-grained crystalline texture. The two main groups are simply chalcedony and chert, but within the group of chalcedony is agate and within the group of chert is jasper.
Chalcedony has an even finer texture, called cryptocrystalline. Chalcedony that is translucent with bands may be called agate.

So I think Chert seems to be more opaque and Chalcedony is more translucent.

That being said and looking at a lot of pics, I think as Nic suggest, perhaps Chalcedony. I know it's hard to tell from a picture. Rocks definitely don't photograph well.

 

[Artfuldodger]

Metaquartzite & Quartzite!
Quartzite is a metamorphic rock formed when quartz-rich sandstone or chert has been exposed to high temperatures and pressures. Quartzite also tends to have a medium grained sugary appearance. The grainy, sandpaper-like surface becomes glassy in appearance.

I'm going to agree with Hillbilly that the orange & white rock in post 7 is Quartzite. I really like it a lot. It's more translucent than I first thought. I got a brighter light and shined it through it. That white band must be quartz as the light went through it really easy.

I appreciate the input. I've got a few smaller pieces that I now am pretty sure are quartzite. They aren't polished by nature though.

 

[Artfuldodger]

I think it's interesting to find so many different rocks from one pile. I need to break the crust of this clay pile with a hoe so that the next hard rain can expose more rocks. I've done been over it about 5 times and I'm running out of discoveries.

I found a piece of quartz with a lot of gold flakes in it. The flakes were real soft. I though it may have been mica but a magnet picked them up so I'm guessing pyrite. Sure fooled me, lol.