I tried it without OptiFine in the latest version of FTB Infinity modpack too (1.8.2), but either in that and in my modpack it is invisible in the Botania Creative Tab, and NEI (and probably in every storage) But it do render fine as a block.

Versions I tested with:
r1.7-201 (Infinity and my modpack has this too)

Can also confirm for the Mana Prism. No optifine, Garden of Glass and Botania 202.

It might be connected with fact that older GFX require square textures and/or power of two dimensions.

I can see it just fine.