Emerald engineered by God for a future city we look forward to...

 And the building of the wall of it was of jasper: 

and the city was pure gold, like unto clear glass. 

And the foundations of the wall of the city were garnished with all manner of precious stones. 

The first foundation was jasper; 

the second, sapphire; the third, a chalcedony;

 the fourth, an emerald; 

The fifth, sardonyx; the sixth, sardius; the seventh, chrysolite; 

the eighth, beryl; the ninth, a topaz; the tenth, a chrysoprasus;

 the eleventh, a jacinth; the twelfth, an amethyst. 

And the twelve gates were twelve pearls; 

every several gate was of one pearl: 

and the street of the city was pure gold, 

as it were transparent glass. 

Revelation 21:18-21