There was some PrC in the Dragon Mag dedicated to dwarves (early 3e issue). I don't think it involved spellcasting, but I don't remember for sure. I do recall that it was focused around earth stuff. It may be exactly what you are looking for. The other option to consider is going the psychic warrior route.
Also, check out the lizardman character (with his skin all black) in RttToEE. I did not DM the campaign but played in it and recall the NPC having some strange earth power (go figure, it was in the earth temple) while using his sword.
As a few other suggestions I would recommend checking the MotP to see if there is anything in there (I recall a berserker that might be along the lines that you are looking for). Also, I think there are templates in their that you might want to look at. Perhaps you could create a PrC that, much like the dragon disciple, worked towards attaining the specific template you had in mind.
Finally, I would second the previous suggestion of taking a level or two in cleric (druid I think might be a bit to natury for you). The few levels of cleric could give you access to two domains with powers and low level spells that might do the trick of mixing in a bit of elemental earth into your character.
In Rokugan there are a few Crab Clan Technique feats that you may be interested in:
Strength of the Earth (+1 HP/level that acts retroactively)
The Mountain Does not Move (I forget, I think it is that you can spend a VP to negate the damage of a single attack against you)
The Mountain Does not Fall (can spend a Void Point to become immune to pretty much any detrimental effect)
IDHMBWM but when i get home I will check to see if Sword and Sorcery has anything at all in the way of PrC's.
Good luck and let me know if you find anything that fits your character concept.