another question

[shalon]

Is it possible to walk into a cave and find a whole bunch of crystals, like quartz and Amethyst? I mean, just sitting in the open air? Or do crystals only grow inside of rocks, under pressure or something?

Has anyone ever seen a bunch of crystals in a cave before?

ok, thanks

[zenas]

Is it possible to walk into a cave and find a whole bunch of crystals, like quartz and Amethyst? I mean, just sitting in the open air? Or do crystals only grow inside of rocks, under pressure or something?

Has anyone ever seen a bunch of crystals in a cave before?

ok, thanks

Of course it is, but a closer examination of the rocks gives better results.
Usually you have to remove the dust or even to dig to recognize them.
At least, this is what i know from the crystals i have find so far.

[ian mckenzie]

I always thought that crystals DID grow in open spaces, rather than within rock, i.e. even crystals "within" rock grew in voids.

[hewhocaves]

Ok.. someone with a bunch of letters behind their degree can further clarify this....

Crystals do form in open spaces. They fill voids between existing rock. If the void is a simple crack or fissure, then it'll look like a vein (like what you expect a silver vein will look like. If there's a big void, then it will fill like a geode. Furthermore crystals follow a particular structure based on their chemical makeup and that's one of the ways you can tell them apart. The crystals that you're used to seeing (particular shapes and forms) have grown within a large void.

Now focusing more on your two suggestions of amethyst and quartz... Crystals require specific chemicals (in addition to the appropriate temperature and pressure) to exist. Quartz, as an example, is SiO2. (one silicon, two oxygen). Limestone is CaCO3 (calcium, carbon and 3 oxygen). Other minerals can seep in (manganese, iron, etc...) but silicon rarely comes in at the temperatures and pressures needed to make quartz. (it requires several hundreds of degrees IIRC and a considerable amount of pressure). In other words, it forms at depths exceeding most if not all caves.

Howewver, all is not lost. There are rather pretty calcite crystals which form in caves. Colloquially, tehy are referred to as 'dogtooth spar' or 'dogtooth crystals'. There's a pic of them on this site:

http://virtual.yosemite.cc.ca.us/ghayes/Black_Chasm.htm

John

[Plethodon]

Is it possible to walk into a cave and find a whole bunch of crystals, like quartz and Amethyst?

Shalon,
A cave maybe sometime like just a big 'vug' or geode. Xls grow inside vugs and geodes all the time. Should you travel south to US sometime go to South Dakota state and Jewel Caves and Sitting Bull Crystal Caverns, and you will see calcite crystals just sitting there. SBCC were them up to a foot long calcite dogteeth spar crystals. Big crystals in Mexico cave look up selenite. and are xls in quartz in book Forti and Hill Cave Minerals of the World. Many big crystals rockhounds buy from miners who find in vugs underground--sometimes mineral being mined sometimes mineral there and traash to owner. Some mines hit caves and find crystals.

So yes is answer to question. "Speleothem" is crystal too, but drippy crystal. Other xls found formed in still water.

[Wayne Harrison]

You mean something like this? This is not photoshoped. It was taken at Davenport Cave, S.D. a few years back:

[bigalpha]

Well, there doesn't have to be a void for crystals to grow. Given high enough pressure and/or temperature, the atoms of minerals will rearrange and form(grow) into crystals.

Though, I assume that you are talking about pretty, shiny crystals? Crystal can have different meanings, so use it carefully. For example, you can have a crystal of plagioclase or hornblende, but they are not exactly shiny and pretty.

Also, amethyst is quartz. Since quartz can come in any color, some colors are given specific names. Purple quartz is amethyst, orange quartz is citrine, and so on and so forth.

As a last note, considerable amount of pressure can be subjective. In geologic view, it doesnt take high pressure or high temperature to form quartz -- but i suppose in speleology, it is high pressure and temperature. Be careful how you choose your words, because it might confuse, or not be very clear to someone who knows all about that kinda thing.

Hope that helps some.

[hewhocaves]

Well, there doesn't have to be a void for crystals to grow. Given high enough pressure and/or temperature, the atoms of minerals will rearrange and form(grow) into crystals.

Though, I assume that you are talking about pretty, shiny crystals? Crystal can have different meanings, so use it carefully. For example, you can have a crystal of plagioclase or hornblende, but they are not exactly shiny and pretty.

Also, amethyst is quartz. Since quartz can come in any color, some colors are given specific names. Purple quartz is amethyst, orange quartz is citrine, and so on and so forth.

As a last note, considerable amount of pressure can be subjective. In geologic view, it doesnt take high pressure or high temperature to form quartz -- but i suppose in speleology, it is high pressure and temperature. Be careful how you choose your words, because it might confuse, or not be very clear to someone who knows all about that kinda thing.

Hope that helps some.

yes, I was trying to keep it simple and consequently cut corners. I did mean crystals in the context that the OP implied. i.e. something pretty with a disctinct, repeatable form. i did also mean pressure and temperature in relation to the common cave environment. Obviously something that is going to metamorphose limestone in marble will not help the cave devlopment because the passage will be destroyed long before then. So while simplification might confuse someone well versed in geology, the full explanation will definately confuse the layman. I left it for the rock people to fill in the "cracks" as it were :)

And yes, amethyst is a variety of quartz. Among other things you get different versions of quartz based on temperature and "impurities" (i.e. othere minerals that work their way in). Here's the big minerologist explanation for the formation of much of the quartz family. Great if you can't sleep at night! :lol:

http://www.minsocam.org/MSA/collectors_ ... icanom.htm

[filox1]

An image better than 1000 words....

[bigalpha]

nice website. it seems as though in my eagerness to contribute to the well-being of society, i have managed to overdo it. tell ya what hewhocaves, why dont ya hire me? i be looking for a place of employment. lol

:)

[CKB69]

Possible,yes.
Probable,no.

You are more likely to find carbonates,sulfates,and,oxides.
Calcite is the most common,and can be just as beautifull as any wall of quartzes.
Same goes for gypsum and its endless variations of forms.

In most cases,formation of silicate minerals happens at temperatures and pressures that are only present at great depths(many kilometers).
There are exceptions,however.

Caves in the Black Hills sometimes contain large areas covered with quartz crystals of considerable size,but quartz can crystallize at comparitively lower pressues and temperatures than many other sillicate minerals.

In enviroments that are more suitable to the formation of gem sillicates,you still are most unlikely to "walk" into a cave(properly termed a "vug"..).
This is due to the presence of "pocket clay" that usually completely fills the pocket.
The clay must be carefully removed and screened for loose crystals.

Often as not,the vug has collapsed at sometime in the past,and you will have to carefully remove these pieces of the old pocket wall,as well.

I have been privledged to see slides of "vugs" that were of staggering proportions!
These vugs were found in the Elmwood mine,famous for it's cacite,sphalerite,flourite,galena,barite specimens.
Imagine a vug,30' high,5' wide,and 50'+ long.
Inside is a crystal wonderland of honey-yellow calcite crystals,4' long.
The calcites are rising out of a carpet of dark reddish-black sphalerites.
Scattered among are pastel blue flourites,and the occasional pure white spray of barite.


I wish I had copies of those slides,as they were spellbinding.
They were taken by a contractor who collected specimens.
They had only a couple of hours between shifts to remove the choicest specimens before the next shift drilled and blasted through the vug,and it went to the crushers!

a few links ;
http://www.corunduminium.com/index.html
http://www.mindat.org/index.php
http://un2sg4.unige.ch/athena/mineral/mineral.html
http://www.webmineral.com/
http://home.earthlink.net/~goke/Cryo-Genie.htm
http://www.gemandmineral.com/peg.html

[shalon]

You guys are reallllllllllly amazing. Thanks especially for the two photos, which almost blew my mind away (I know it's cheesy, but I had to cry a little). I couldn't believe how beautiful they were, and how it fit the picture that I had in my minds eye. What I've come to learn from all of you - is that anything that I could dream of being possible - IS. And that I just need to trust my intuition. But I will keep on asking questions when I forget that - again...

[hewhocaves]

hey bigalpha,

I'd love to give you a job, but i'm lookingfor one as well! ;)

john

[bigalpha]

well dang hewhocaves -- how am i supposed to get ahead in life if other people won't bend over backwards for me, cater to my needs, and do what i tell them to?

sheesh

[hewhocaves]

well dang hewhocaves -- how am i supposed to get ahead in life if other people won't bend over backwards for me, cater to my needs, and do what i tell them to?

sheesh

you missed your calling.... :)
but you can still run for president. there's another election in three years ROFL.

John

I kid... I kid....