This is London Blue topaz in a 4mm rose cut cushion. Lovely petrol blue colour. Precise faceting, and the material is clean.
Shape: Square cushion
Cut: Rose cut cabochon
Approx carats per stone: 0.4
Country of Origin: Brazilian material, treated in the US
Treatment: Irradiated (for more information please see my 'Gemstone Information' page)
Clarity: Eye clean