Twilight Sparkle and the Crystal Heart Spell
The chapter book Twilight Sparkle and the Crystal Heart Spell describes Twilight's new status in chapter 1, "A Crown Achievement": "Twilight had received her very own set of wings. Real Pegasus wings! She was officially a part of a special breed of pony called an Alicorn. This meant that Twilight was now able to harness the magical powers of the Unicorns, the flight abilities of the Pegasi, and the strength of a good, true heart of an Earth Pony."

Theories of Magic: Earth Ponies

Earth-pony are stunger (then the other race)
faster on hoof (then the other race)
can heal faster (then the other race)
have extra censes
their other censes are stronger
they are a bit bigger
faster mitabolisem
Earth-pony are good at 3 things (will the other races are only good at 2 things)

I like to think that Earth Ponies have healing magic.

Sure, why not? Maybe Luna gets her dream magic from her earth pony part.

come to think of it, what if the sisters get their sun/moon stuff from the pegasus part?

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I like to think that Earth Ponies have healing magic.

for me, I thing the just heal faster them others

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come to think of it, what if the sisters get their sun/moon stuff from the pegasus part?

maybe it's the earth-pony part

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But... it was unicorns who moved them in the past. It even says in the beginning, that the older sister used her unicorn magic to bring out the sun.

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Oops! I forgot ^^'