How does "Convert Gems" work in Diablo 3?

How does Convert Gems work, and what is it useful for?

Convert Gems
Transforms 9 gems of one color into another. The resulting gem color varies depending on reagent used. You can buy gem reagents from Squirt the Peddler in Act 2.

Solution 1:

Gem conversion is not really an issue until you progress into the endgame of Diablo 3.

Once there, you will find that it is essential to begin augmenting your items in order to move upwards in the Greater Rifts.

Each augment requires 3 Flawless Royal gems, and as you begin to upgrade your items you will run out of the main gems used for your main stat.

At this point, it is important to convert your off stat gems into main stat ones.

As the recipe states, you use 9 of one type, and get 9 of another. How this works is that all 9 must be of the same rarity (for example, all must be Imperial). You then include a Gem Essence of the type you want to convert to.

I would suggest not upgrading your gems too far prior to conversion, because it can be easy to only end up with for example 5 Flawless Royal gems of one type, and then not be able to Convert them (as it must be 9).

While the Gem Essence does cost 500k gold, at the point you need to be doing these you should have billions. If you lack gold, you should look into placing a Puzzling Ring into the cube and getting Greed's Gem.