Question: The [Stone Warder](http://www.d20pfsrd.com/classes/core-classes/sorcerer/archetypes/paizo-sorcerer-archetypes/stone-warder-sorcerer/) archetype for Sorcerer includes:

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> Power of Stone (Su)
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> A stone warder draws power from natural rock, and gains a +1 bonus to her caster level when in hills, mountains, or underground terrain. This bonus increases to +2 at 5th level, and by an additional 1 every 5 sorcerer levels thereafter. **However, this strong elemental tie prevents a stone warder from casting spells that have the air, cold, electricity, fire, or water descriptor.**
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Emphasis added. Would taking a spell with the denied descriptors, but casting it with the [earth] tag, be a valid choice or am I barred from selecting any of these spells?

For example, the Elemental (earth) Bloodline Arcana allows me to "Whenever you cast a spell that deals energy damage, you can change the type of damage to match the type of your bloodline. **This also changes the spell’s type to match the type of your bloodline.**" and the Elemental Spell metamagic has similar wording. Would I be able to take Fireball as a spell and cast it as Evocation [earth]?

Answer: 
The [Magic](http://www.d20pfsrd.com/magic/) rules don't mention "spell type" or anything close to it at all. Then the wording for the elemental bloodline arcana must be wrong, and "spell's type" may refer to spell descriptor. Then your damaging spells should all get the acid or earth descriptor in place of their original elemental descriptor and deal acid damage and you should be able to cast them as a stone warder.
Yes, it's a valid choice.
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You can learn those spells just fine, the ability simply prevents you from **casting** spells with those descriptors. Nothing prevents you from using extraordinary or supernatural abilities that emulate those spells, or from learning those spells, or even from activating magic items that have those spells, as long as they arent spell trigger or spell completation (scrolls and wands).

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> However, this strong elemental tie prevents a stone warder from **casting spells** that have the air, cold, electricity, fire, or water descriptor.
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This means you can learn [Fireball](http://paizo.com/pathfinderRPG/prd/coreRulebook/spells/fireball.html) just fine, as it has the [fire] descriptor, but **you cannot cast** fireball with the [fire] descriptor, **you must change it to [earth] in order to be able to cast it**.