I did a little checking to make sure and The Heart of Candracar is only gem the team has. It's mean to summon the girls battle forms and magnify their powers.
Phew, I though I'd need to get myself one of those round inflatable doughnut chairs.
I'd say the first seven or eight arcs of the comic are worth a read, but where the show was abruptly cut off right as it hit its stride, the comics have the opposite problem. They start out great, but wind up dragging on and on, losing their initial strength and quality until by the end it's painfully vapid.