This beautiful collection is often mislabeled, As it bares a resemblance to Tiffany stone, which it is not, It is Sagenitic Fluorite, otherwise known as Opalized Fluorite. Tiffany stone is only found in Utah while this material is found in China, which is where I have sourced it. 
These pieces have a beautiful mix of purple, white, and green, with Striking intersecting colours and currently marketed as Rare. 
Sagenitic fluorite is the mineral form of calcium fluoride. It crystallizes in isometric cubic habit. It is relatively soft, 4 on the Mohs.
It is said to improve concentration and focus, so a great stone for students and teachers. Fluorite is considered to be the genius stone, providing mental clarity and awareness. 
It also is a great healers stone with its purple colour, and has a very calming Harmonizing energy too.

Sagenitic Fluorite