Rocks and Minerals B/C

[SciBomb97]

I've been finding mixed definitions on this––what is Jasper? An opaque chalcedony? An opaque chalcedony with ferric inclusions? A chert?

And if it's debatable, what definition would you use to identify it in competition?

From what I understand, jasper's just a variety of chert. Basically, it's chert that isn't black (that's flint) or white. It's typically red or green.

Jasper is also usually speckled with white inclusions.

[sciencegeek100]

I've been finding mixed definitions on this––what is Jasper? An opaque chalcedony? An opaque chalcedony with ferric inclusions? A chert?

And if it's debatable, what definition would you use to identify it in competition?

From what I understand, jasper's just a variety of chert. Basically, it's chert that isn't black (that's flint) or white. It's typically red or green.

Jasper is also usually speckled with white inclusions.

its usually red not speckled with white inclusion

I was 2nd at Nationals in 2008 as a freshman

[crazyfloboe]

I've been finding mixed definitions on this––what is Jasper? An opaque chalcedony? An opaque chalcedony with ferric inclusions? A chert?

And if it's debatable, what definition would you use to identify it in competition?

From what I understand, jasper's just a variety of chert. Basically, it's chert that isn't black (that's flint) or white. It's typically red or green.

Ummm...Jasper is a variety of Quartz not Chert

[tuftedtitmouse12]

I'm pretty sure I've heard it for both... But to be on the safe side, I'd go with gneiss's info...

[quizbowl]

I'm pretty sure I've heard it for both... But to be on the safe side, I'd go with gneiss's info...

Actually, everyone so far is wrong! Jasper is a form of Chalcedony.

[SciBomb97]

I'm pretty sure I've heard it for both... But to be on the safe side, I'd go with gneiss's info...

Actually, everyone so far is wrong! Jasper is a form of Chalcedony.

You got that from Wikipedia, didn't you? Different Wikipedia pages seem to be conflicting on this... THIS page says that jasper is a variety of chert under the "Varieties of Chert" heading while THIS page says that it's a variety of chalcedony while THIS page says that jasper, chalcedony, and chert are all just different forms of microcrystalline quartz under the "Varieties (according to microstructure)" subheading.
In fact, chert, chalcedony, and jasper are all just different forms of quartz. Of that I am sure.

[quizbowl]

I'm pretty sure I've heard it for both... But to be on the safe side, I'd go with gneiss's info...

Actually, everyone so far is wrong! Jasper is a form of Chalcedony.

You got that from Wikipedia, didn't you? Different Wikipedia pages seem to be conflicting on this... THIS page says that jasper is a variety of chert under the "Varieties of Chert" heading while THIS page says that it's a variety of chalcedony while THIS page says that jasper, chalcedony, and chert are all just different forms of microcrystalline quartz under the "Varieties (according to microstructure)" subheading.
In fact, chert, chalcedony, and jasper are all just different forms of quartz. Of that I am sure.

Not really. Chalcedony is really an amalgamation of both quartz and mogamite. While both are SiO2, mogamite is really a polymorph of quartz. Yes, it is a silica mineral, but I personally don't consider it a variety of quartz. However, the list trumps all interpretation, so while we might argue for days on end over the true chemical nature of these minerals, the list is all that counts.

[crazyfloboe]

Werll, accordiong to the offical list for Nats 2012. Its Quartz, and im trusting that list and that list only.

[LoopQuantumGravity]

Source:http://webmineral.com/data/Quartz.shtml
According to this, jasper is red or brown chalcedony.
Chalcedony is microcrystalline quartz. Also, other sources have said that it also contains moganite (a monoclinic silica mineral)
Chert is similar, only it is cryptocrystalline (smaller crystals).

[gneissisnice]

Source:http://webmineral.com/data/Quartz.shtml
According to this, jasper is red or brown chalcedony.
Chalcedony is microcrystalline quartz. Also, other sources have said that it also contains moganite (a monoclinic silica mineral)
Chert is similar, only it is cryptocrystalline (smaller crystals).

Chalcedony is microcrystalline and chert/flint is cryptocrystalline. What that means that is that chalcedony has tiny crystals, while chert has crystals so small that you can't see them at all, making it look more like there aren't any.

I always learned that jasper was red or brown chert, not chalcedony, but I suppose there's still some grey area there. Easier just to say that jasper is red micro- or cryptocrystalline quartz and call it a day.