So I bought a pretty nice collection of stones but cut and rough and I want to think this is alexandrite but I have not found a ton of information so far.
Very much a blueish green in normal light then purple ish. Glows bright red under both 395 and 365. Also bright red under Chelsey filter
Can you describe what “normal light” you used? And what light was used for the second image?
The matrix looks kind of like biotite. It would be good to get some additional images of the matrix as well, as that can help with origin. With the crystals-in-matrix, it will be somewhat challenging to do more definitive diagnostic tests. A polariscope, hand-held spectrometer, and refractometer could provide good information, but might be difficult to perform.
That being said, I suggest this particular specimen be sent to a gemology lab. This will cost some money but, you have a very interesting mineral specimen, and I think (IMHO) it would be worth the cost. Another option would be to approach a local University’s geology/mineralogy department. They can perform some of the same diagnostic tests that a gemology lab can do, however, they may or may not be willing to classify it.
That is a really interesting specimen you have. Please tell us what you find out! Very curious!
Agree…matrix looks like biotite schist. Aluminous schists and derived pegmatities from partial melting can host alexandrite, emerald. Agree that this should be looked at by a mineralogist.
I do not know where it came from exactly. There little to no info or organization to the collection but is obvious that multiple things came from many place all across the world
it’s a problem with a lot of stones- the provenance, which would give you valuable information is always rarely known…the geological setting of the any mineral sample or stone gives the most clues to it’s identity and value. Colored stones are sold in mixed lots and no one knows where they came from. Having a great mineral specimen would be worth more if the locale is known.
Does the fluoresced color persist for any period of time after UV exposure? That is, does it exhibit tenebrescence? If so, it may be in the solidite family (sp?). Just a guess, but the one pic of the purple color in what appears to be natural light appears similar to what this effect looks like with minerals like hackmanite, which I believe is in that family.
(Photochromism - Wikipedia)
I have never seen Alexandrite in the rough before (let alone in a matrix) but I’m curious if this couldn’t be Green Sapphire ?
Obviously, without knowing the size of these crystals or the entire specimen and without seeing any specific Crystal Form it’s hard to tell what it is but Green Sapphires (Corundum) will also Fluoresce Red under UV and they can also be found in a Schist.
Sodalite family minerals are incompatible with high silica peraluminous environments. Your previous find of Hackmanite came from a unique place. (I hope that I have the right person, as I can’t remember for sure who posted the hackmanite photo)… it’s an interesting question about the specimen being corundum… it’s a possibility.
You brought up a good question. You are absolutely right that corundum can be found in schists. Mica schists, including muscovite, and two mica schists can host corundum. The mica indicates a peraluminous state which can result in the crystalization of corundum. Other accessory minerals are aluminous… kyanite, garnet, staurolite, sillimanite, cordierite. Metamorphic grade is medium to lower end of high…the schists are aluminous to peraluminous…alexandrite requires that beryllium. chromium be present. That is an unusual combination, and what makes alexandrite rare. beryllium is held within the last of metamorphic fluids to be crystallized. adding chromium requires a parental mafic mineral. These are extremely rare combinations.
hi there every one . this is a rather interesting peace as i deal with a lot of rough and collector’s grad alexandrite specimens quite often, and thou this all looks wright for an alexandrite there are may different types of color changing and color shifting gems in the corundum / chrysoberyl and garnet families. A few other gems in the family tree branches. It is however important to remember that alexandrite is extremally rear and deposited in only a few places warld wide, So in order to be totally shore you would have to have it tested by density specific gravity and mineral content as we have had some incident’s here in Africa with materials from Zimbabwe that do change color but are not alexandrite, the specimen in question is perfectly placed from appearance and color shift to be the correct gem type of alexandrite.