1.51 ct. Leucite
- Color: Faint Yellow
- Clarity: Slightly Included
- Origin: Near Ostia, Italy
- Cut: Cushion Mixed
- Treatments: None
- Measurements: 8.6 x 7.1 mm
An extremely unique gem species with fine gems in excess of 1 carat being particularly rare. At first glance, you may think this is just simply another rare colorless gem material, but the attraction of Leucite resides in a very unique optical phenomenon. Firstly, it is one of the very few gems having an isometric crystal form (like garnet or diamond) that actually has a birefringence - the result of a complex process whereby it forms isometrically at high temps and changes to a tetragonal structure as it cools without changing the outward crystal structure.
Secondly, as a consequence of its lamellar structure and resulting diffraction, Leucite can have an opalescent quality that will produce a color flash. Hence, you have what appears to be an opal-like 'play-of-color'. There is no other gem material that comes close to imitating this effect. This lovely example is a fine and large cushion and has an excellent color flash. Just touch the gem with a little direct lighting and the unexpected flash becomes apparent. The intensity of the spectral flash varies considerably from stone to stone and is quite strong in this example.