Shiny Stones usually provide three ores when processed in a Stone Grinder. However, in rare occasions, they can also drop Opals. Due to the rare nature of Shiny Stones, the chances of obtaining Opals from them is quite low.
Thunder Eggs can sometimes spawn in a map following a huge thunderstrike. These eggs can then be broken using a pickaxe or they can be thrown into the water to reveal the Opals inside. A Thunder Egg spawn is highly based on RNG and is a rare event on its own, but once you obtain one, it’s a guaranteed four Opals for your inventory.
Be advised that selling the Thunder Egg might fetch a higher price depending on its weight when compared to selling the Opals it contains, so make sure to have the egg weighed at John’s Goods first before cracking it.
Quarries are a good passive source of ores and components, and it can also fetch Opals from time to time. Quarries can be commissioned from Franklyn and is quite easy to set up. A huge field of Quarries can definitely increase the chances of getting Opals without doing much work in the long run.
Opals are mainly considered as valuable or sellable items to get a huge amount of Dinks. Selling one Opal over at John’s Goods will give 15,000 Dinks a piece (the selling price can be affected by the Commerce License).
In the current build of the game, Opals are not used in other recipes or blueprints; the only other thing that you can do with them is to display them on Wooden Signs, which don’t really use up the Opal. We’re hoping that in future updates, we’ll get to see more things that can be done with this gemstone.