Need Help On The Cut Of A Tourmaline

[pwsg07]

I am interested in a round tourmaline. The dimensions are 8.76mm x 5.55mm(depth). Since tourmaline is a lower RI stone, is this stone too shallow? The blue tourmaline shows some green color under the sun. Is it bad for blue tourmaline? How can I check the brilliance of the stone? Should I ask the vendor use a penlight to shine on the stone and take a photo? Thank you so much.