Can you identify this quartz-like rock?

Question

Hello. Here is an image of a crystal that I was given as a gift. I have no information about the item, I initially labeled it as quartz, but I examined the crystal structure and it does not seem consistent with a quartz pattern. It is possible that this is a synthetic crystal; I really have no idea.

Here is a link to an image of it:

http://img201.imageshack.us/img201/5024/dsc01242da9.jpg

http://img201.imageshack.us/img201/3964/dsc01241uz9.jpg

http://img244.imageshack.us/img244/2791/dsc01240sa9.jpg

http://img213.imageshack.us/img213/4179/dsc01243nn4.jpg

Thanks to anyone who has a good guess!

Answer 1

Hello everyone, this is the same fellow who asked this question. My original yahoo answers account was deleted after I switched my ISP, because AT&T is evil.

Thanks to everyone for their input. I am very sorry that I am unable to pick a best answer, but I cannot access the account that I asked this question under. Thank you all for being so understanding.

I tested the calcite theory with some sulfuric acid I I did get a slight reaction, so that answer appears to be correct. Nice call!

I'll probably be asking some more identification questions in the future if I ever get my points transferred.

Answer 2

Looks like calcite to me but identification is not one of my strong points so i could be wrong.

Answer 3

I am almost certain that your specimen is calcite twinned crystals...

http://www.minservice.com/store/Scripts/...

Photo of calcite that is not twinned.  You can see the same "parallelogram structure" seen in your photos (particularly your last photo).  Calcium has a hardness of 3 and is soft enough to be scratched by quartz.

http://www-gems.com/gems/catalog/images/...

Answer 4

Without having the specimen in one's hands it is difficult to give a definitive answer but the crystal group in the pictures has an absolutely typical structure of Selenite which is a form of Gypsum CaSO4.2H2O   It is very common in the area where I grew up and specimens of it formed a large part of my childhood collection. A simple test to distinguish it from calcite, which it can closely resemble, is to touch an out of the way area of the specimen with a drop of acid - calcite will fizz selenite will not react.

Hope that helps a little.

Answer 5

your right, it does have the color of quarts..but its hard to tell its plain of cleavage. you can do a simple test to see if its halite, l**k it, if it tastes salty its halite, it looks like it has 2 plains of cleavage so try to findout what crystals have that amount of cleavage