A historic gem imitation, Soude Quartz is sometimes also called Soude Emerald.

As opposed to a doublet, Soude Quartz is a triplet with both a crown and pavillion of colourless natural Quartz.
All of the stones colour is due to a layer of green-coloured glass in the centre of the stone and which comprises its girdle.

The junction between the three sections is clearly visible with just slight magnification, as shown in image 4.
Image 5 shows how the colourless portions of the stone becomes visible when the stone is viewed from some angles, although it appears a convincing green colour when viewed face on (image 5).

Flattened air bubbles trapped within the adhesive layers can be seen by eye, and more clearly displayed in my slightly magnified image 6.

weight:  19.95 carats
shape:    Square emerald cut
dimensions:   16.80 x 16.79 x 11.24 mm