Tinker's Construct in general does not include gems as a tool material, but rather as a tool modifier.
Diamonds and emeralds for example add bonus stats to an existing tool instead of being something you can make tools out of.

Applying a similar logic to the gems added by this mod (epidote etc) would be nice to benefit cohesion, thanks!

i'll have you remember tinker already had diamond and emerald as modifier in 1.12, I didn't do it in 1.12, I won't do it now.

you're free to change that with a datapack.

Fair enough, I figured 1.12 is a long enough time span where some designs might be up for debate, but it is your mod and your decision to keep it as it is, so I won’t argue there.
Thank you for your consideration.

I will not do that. I've been doing gem materials since the 1.12 days, i'm not gonna change it just for it to be "coherent" with tinker.

heheheha

That's a shame - I think it would be cool to be able to apply epidote's critical damage boost to existing tools rather than as a weird handle made of cast gems, as a sidegrade to emeralds and diamonds (along with the other mod gems of course).

For what it's worth having it be that way since 1.12 makes less sense; Tinker's Construct has fundamentally changed a great deal since those versions, what may have fit well back then is very much out of place now.