Jewels spawn randomly on your properties and can be put into the slots of your properties to gain extra essence and materials.
Crafting
You can craft your jewels so they become more powerful
3x tier 1 of the same color produces a tier 2 jewel.
Tier 2 Jewels can be used to create special jewels:
Purple = Ochre + Blue
Orange = Grey + Sandy
Sunrise = Blue + Ochre + Grey
Sunset = Sand + Purple + Orange
Jamaica = Black + Yellow + Green
Upgrading
You can upgrade your Jewels according to the schedule below
8 Shards = Cloudy
25 Shards = Common
50 Shards = Clear
84 shards = Luminous