I can't meld a Gatherer's Grasp Materia III to my Boarskin Survival Belt.

The option to meld the Gatherer's Grasp Materia III is greyed out.
I have the Catalyst, and I am a LV50 Leatherworker.
I can meld other materia to it (But I choose not to)
There isn't a single materia melded onto it.
And, I bought the Boarskin Survival Belt off the marketboard.

Any idea why I can't meld a Gather's Grasp Materia III to the Boarskin Survival Belt?