Jade

Jade is a cyan damage special poison gem made with normal emerald, normal opal and flawed sapphire.

Like other minor pieces, jade can be upgraded twice. The second upgrade's ability to obtain additional gold makes it vital in survival mode, amounting to about level*2 gold in later teens, and twice that in twenties. The level refers to gameplay level, not jade's level, so level 0 jade will yield as much gold as level 20.

In the Javascript version released in 2021, the chance of getting gold is much higher: reportedly 10% chance per hit instead of 1% chance in the original Flash version.

If one follows the strategy of placing stunning gems out of the range of fliers, there is limited space available in lower left corner:

Lucky Asian Jades placed entirely in light cyan area will not hit bats.