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Identity Helpsylvite??

18th Mar 2007 19:58 UTCElizabeth McRorie

I picked this up in Tucson this year and have been trying to decide what it is. It was sold me as halite from India. But it doesn't look like any halite I have ever seen. I got it anyway, just because I thought it was neat. Right now, I am now leaning toward it being sylvite. (In the halide family, like halite and florite.)

Facts:

14" x 6" x 4"

weighs about 14 lbs

dissolves in water

tastes nasty/salty.. not like my other halite that just tastes salty

very fragile

scratches white

mohs - 2

I think it's octahedral but I am not very good at crystal systems :)

transparant to translucent crystals..top crystals are tipped clear with what looks like purple phantoms inside

I have searched the internet high and low and can't find anything like it.

18th Mar 2007 20:02 UTCElizabeth McRorie

and a close up

18th Mar 2007 20:03 UTCElizabeth McRorie

and a close up of the tip

18th Mar 2007 20:16 UTCFranz Bernhard Expert

Could be lab-grown, chromium-bearing alum K(Al,Cr)(SO4)2 . 12H2O

Franz Bernhard

18th Mar 2007 22:20 UTCDana Morong

A beaut of a specimen even if it is Cr-bearing alum. I used to grow a few but never as large as this. If it is indeed alum, a very tiny sample knocked off (some unobtrusive place such as the bottom) could be put into test tube and gently heated, see whether it gives off a bit of steam, if it contains water of hydration (the "12H2O" at the end of the chemical formula). And if so, then be careful where you store it. I had some I put in the window once and the outsides dried up slightly, making a white powdery deposit on its outside. Maybe it was too dry air or maybe too much heat. Anyway, the ones (single crystals up to an inch) stored normally and mostly in the shade (rather than in constant sunlight) didn't seem to alter, and were okay.

When I first started out in the hobby I was given an old collection, included was an octahedral white crystal I thought was sylvite but later I found was alum. That was educational for me.

Nice photo of some nice crystals.

19th Mar 2007 02:13 UTCAlan Plante

Yes, most likely lab-grown alum xls.

Alan

19th Mar 2007 12:03 UTCElizabeth McRorie

Thank you! so it's what they are calling cermikite? Well, I still got a bargain even if it's fake..didn't pay anything near what they are asking for a little specimen of it on eBay AND I got a great lesson on minerals trying to figure it out.

19th Mar 2007 15:19 UTCAlan Plante

Hi Elizabeth

"Cermikite" appears to be another made-up marketing name. I don't find it in any of my mineral references. Did you try looking it up here at Mindat? (I haven't given that a shot yet.) It might already be entered here, with an explanation of what it refers to.

Regards

Alan

19th Mar 2007 15:22 UTCAlan Plante

It's not entered into Mindat yet, but when I Googled it I came up with references to posts on this board - saying that it is a name that has been given to lab-grown chrome alum xls. So you hit the nail right on the head!

:~}

Alan

19th Mar 2007 15:53 UTCUwe Kolitsch Manager

"Cermikite" is misspelt Tschermigite (ammonium aluminium member of the alum group).

19th Mar 2007 20:04 UTCAlan Plante

Either spelling, it should not be applied to lab-grown xls.

:~}

Alan

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