Topaz is a mineral in Stardew Valley that most villagers like as a gift. There are several different ways to get Topaz, such as digging through garbage cans or treasure chests, but that's really random. The most likely way to find it is by going to the mines and looking for it.
How to farm Topaz in Stardew Valley
There is no special Topaz rock or stone to destroy. Most players have found it by mining purple rocks and rocks with yellow stones coming out of them. Although it does not happen enough to call one a preference, you're very likely to find Topaz if you keep mining all of the stones found in the mines.
Farming Topaz is as simple as mining every rock on a floor that is level 5 or lower. Stick to one floor because you can kill the enemies quickly and can just focus on mining every rock in sight. You will be able to finish a floor and a half before having to go to bed.