Need help identifying this blue crystal

[Geminrock]

[d_day]

It looks like fluorite, but I’ve never seen it with that structure, so I just don’t know.

[Beeper Bob]

Possible blue sapphire. What area did you find it in? what is the hardness?

[clay]

It looks to me like heat treated zircon. The fact that it fits the right Tetragonal crystal system, color and with an adamantine, greasy and vitreous  luster is why I see that in the picture. The actual crystal form is suspiciously perfect for a natural zircon. That's all based on the appearance in a photo. Without more information it could also be a child's plastic bauble.

The crystal form clearly shows it couldn't be a sapphire. Corundum belongs to the Trigonal crystal system. Corundum never crystallizes in the form in the picture and the crystal in the picture has no identifiable stepping along the c axis as sapphire does. There are only two crystallographic forms for corundum (sapphire) and the picture doesn't fit either.

Fluorite? Sure looks like it could be from the picture. Color is a possibility. Twinned Isometric system crystals of fluorite can take a very similar form.

The fact is none of us can tell what this is without more information. Pictures just lead to speculation which really isn't going to help identify the mineral.

[4meter]

Very beautiful blue stone.   I’m with clay, it may be a treated zircon stone.  Other candidates are a blue diamond or a treated spinel stone.  All three of the above have the correct forms.  Might not to rule out cut, treated glass.