Thank Golnaz! Are these tests difficult? Do you know any published publications/instructions/methodologies with identification keys of mnerals?

It is always a bit difficult to identify a mineral from a picture (properties as lustre, shape of crystals and transparency-opacity vary with light and perspective). Any clue about the hardness of the mineral (this is an easy test to be done in a school)? Is it fluorescent under UV light? Given the abundance and the cubic shape of some crystals I would say that at least one of the minerals in the picture could be fluorite. Also it seems there is a second mineral with micaceous lustre. It is a pity that such a nice specimen has no label with the name and locality on it. I hope this was useful.

It looks like Kyanite. Please see http://en.wikipedia.org/wiki/Kyanite for more information on Kyanite. Can you let us know exactly from which place it has been picked up?

Will try to get some information and a small sample to test it (or send it to someone interested in this beauty :-)

Concerning the form of the crystals (needle like) and the colour it could be rubellite, which is the red or pinkish-red variety of tourmaline. You can use X-ray diffraction, where only a very small amount of powder of one of these nice crystals is needed, to identify the mineral.

I agree with Ms Susan Schorr that an XRD test is the most suitable method because it is easy (a piece of the sample must be ground in an agate mortar), relatively cheap, requires a small amount of sample (few grams) and it is in most cases unequivocal (you compare your results with a database and you get the mineral name). Try also to make an easy hardness test: try to make a scratch on it using a knife (does a scratch appear on the mineral surface?), and to scratch a piece of glass using the mineral (does a scratch appear on the glass surface?).

Harndness is also a good method for a first guess. Rubellite has the hardness of 7-7.5 (Moh's scale), thus your mineral should be able to scratch a glass surface. Others suggested amethyst (I have strong doubts), which cannot be disinguished by the hardness, because it's harness is also 7.

By just looking at the picture I would say - kyanite - and not - amethyst- simply because amethyst doesen have needle like habitus like i can see on this image. Ether way you would need to do some additional tests

I am sorry, but kyanite is blue, mostly.

Perhaps Purple fluorite

Fluorite is a cubic mineral and never shows a needle-lie shape - sorry!

Are u sure not fluorite, can u tel me from were collected this sample

I am sorry. Nobody knows. It is from an old school collection. No label, no information. I have only this picture, will chceck it (the hardness, take better pictures and a smal sample) in few days.

I also saw cube-shaped crystals, both small-sized (lower left) and larger-sized (upper left, only the corners are seen). The needles described by some contributors here seemed some growth features to me. To continue with the hardness comments by Ms Schorr, if the sample is scratched by a knife, and not by a coin (and does not scratch the glass), it has the hardness of fluorite.

The photo is not so much usefull in definition of the mineral.. in any case:

You can have many ways to solve the problems:

Hardness: Rubellite (a Tourmaline) > Fluorite

XRD: a diffraction on powder is very usefull (and powerfull)

S.E.M. with EDS: just a spot in BSE or SE and observe composition

Photo: a better photo will help to better observe mineral shape!

In any case: cube-shape (if it is cube) is common in fluorite!

Will ask the teacher.

After looking very carefully in detail on an enlarged figure, I would agree with Christiane about the cube shaped crystals (very difficult to see). If you send me a few mg I can perform an XRD measurement which will indentify the mineral (or minerals?) clearly.

Ok, we waiting the result of minerals analysis

Many thanks! The teacher said I can take small sample.

I will spend one week at IGB in Berlin (April 7.-11.) so I can deliver it to Helmholz-Zentrum for proffessor Schorr.

I can also send it to dr. Yersel. (I am waiting the address in private message.)

Dear Peter: We wait then the results of the analyses!

It is Fluorite.

It is Fluorite.

IF it is not an uncommon mineral and is cubic, it coud be fluorite. knrao

It can not be amethyst as it appears to have well deveoped cleavages. knrao

I am in agreement with those who recommended XRD, but for me, because of its cubic habit, well developed cleavage and spicial shap, it is very simillar to Halite. But I am loking for XRD results, if any.

This colour, size of the specimen and obvious cubic crystals points to fluorite. XRD seems a little over the top at an initial stage as there are three additional tests that can be done that are far easier and conclusive. Fluorite is softer than glass but harder than a penny; it has an obvious cleavage and since there are visible crystals a small break should make the cleavage obvious; purple fluorite usually fluoresces blue under long wave UV (most common type of lamp used on stamps, money, etc.). Halite is even softer and is water soluable. Also halite tastes salty. Fluorite has no taste. Anyone should be able to do these simple tests. If after these tests the results prove negative for either fluorite or halite, then showing a sample to an experienced mineralogist would be a logical step. He/she should be able from experience (especially if they are a collections curator at a museum) be able to make a visual determination and it this is not possible to then recommend a more elaborate test. EDS would be much easier and quicker to eliminate common minerals like fluorite before going to XRD. Hope this helps. One last item: if you know where the specimen was found, a simple search on the locality should give you information on the minerals that occur there. If fluorite is one of them you would almost surely have that mineral. (note: this seems to be a large specimen and there are very few minerals with this colour so the most common is also the most likely.

Dear Erkan

Are you really sure of your results? Clinochlore is an alumina-magnesium-silicate, and Cr-Clinochlore is purple. And this mineral instead is violet.

But above all Clinochlore is monoclinic prismatic.

And the mineral in the photo seems to show us part of its cubic shape.

Sorry for doubts, but this mineral seems very far to be a clinochlore.

Ciao

F

Dear Erkan

what kind of analyses do you have produced?

powdering and XRD? or Microprobe?

I'm just surprised that such morfology revealed a chlinoclore!!

Ciao

F

Could it be the piemontite epidote?

michele

The color and cubic form is typical for Fluorite. The hardness should be 4. Try scratch it with a piece of glass and see if it scratch calcite.

Does the teacher know where the sample came from?  Mineral occurrence is very valuable in figuring out what the mineral is.  If it comes from a location that is well-known for having fluorite, I'd say it was fluorite.  Likely the teacher doesn't have the resources to get the sample analyzed by analytical equipment.

Unfortunately the teacher does not know where is the mineral from.

Prof. Susan Schorr sent me a figure of the X-ray diffraction measurements as well as the comparison with minerals from the database today (attached). Prof. Schorr and her PhD student Kai Neldner will also  will now confirm the result with the determination of the chemical composition of the different phases with the Electron Microprobe system. I amlooking forward to see the results!