This is a pearlescent lime-green Prehnite from Africa, cut as a cabochon measuring 19 x 14 x 7 mm and weighing 15.08 carats. The oval shape of this stone makes it versatile enough to work as a focal for a pendant, a brooch, possibly even a bracelet or a statement ring if the stone is given some protection. A well-polished piece with a luminous colour, this gem would be outstanding when set either with bright metals like white gold or platinum, or even when contrasted against the darker metals like oxidized silver or copper.
The pictures give an idea of how the gemstone looks under various lighting conditions and different backgrounds. The last picture shows the detail of the gem in profile.
Prehnite has a hardness of 6.0 to 6.5 on the Mohs Scale. Prehnite is known in China as "Grape Jade" due to its nodular crystal habit which can appear like a bunch of pale-green grapes.