It's quite a gorgeous find on Rarity's spelunking tour, even if she'll probably need to break the stone into pieces if she wants to. Then again apart from the concerns most ponies may have over big glowy gems underground which could be magic — or at least support for the chamber — one can imagine her finding the large icy "heart" of the cave, held fast by the stalagmites and stalactites may be just too beautiful in its whole form for even the fashion pony to break apart. It would be such a shame to take apart something so breathtakingly and wondrous.
Along with the wonderful glow lighting the cave, icy tones, Rarity seems to be glowing much warmer in her colors. Could it be a trick of light scattering, or is her soul warmed so much by the site that she's mesmerized. Maybe she'll keep this discovery a secret, lest any other ponies try to claim it, but for now she seems to be reveling in the wondrous beauty, lost in its beauty. With any luck, it may at least give her inspiration.