Hi Feather!
Lovely little poem, very evocative; the imagery is vivid and original, well done!
I'm going to offer you some line-edit suggestions concerning the language (some sentences are not exactly correct), but you're obviously free to deal with it as you choose

Split the darkness on the floor of mirrors on which
"on which" is redundant with "on the floor": the constructions are too similar and that somehow dissolves the power of the image. It's also a pity to end this first verse and it's vivid imagery on something as weak as "on which," as it doesn't really lead anywhere.
The soul breaks the Cristal of the lucky belief.
- That's way too many
the's, which is good neither for rhythm nor comprehension. I would advise to play with plurals to solve that problem; and it depends on what you mean, but in English not every noun need to be preceded by an determinant
- In my opinion, the temporality would have more depth if you did not stick to the present tense in the second verse, but this is very subjective.
- Also, small mistake: "Cristal" is French, English would be "Crystal."
When the crazy dance of the tree offers the sky's music to the child every night.
- I'm not too sure about the purpose of this "When," but then again that might be poetic license!
- Too many determinants as well (4 in one line!).
- "Sky's music" is a bit odd, I would suggest "music of the sky."
- As for "the crazy dance of the tree," I would settle for "the crazy dancing of the tree," which brings the action closer to us.
- I also think the verse is a wee bit long compared to the others, which doesn't work that well in my opinion. I think you could try different breaks in that line so as to make the rhythm more gripping.
That is the cry of hope and the future seeing.
-"That is" seems like a calque of the French "C'est" -- it doesn't work too well in English. Moreover, since you have two elements afterwards, you need to use the plural.
- I'm not too sure about the determinants either, I don't think they flow very well.
- What do you mean by "the future seeing"?
- I actually find this last line to be not as strong as the rest of the poem; a bit too explicative, I guess, whereas the rest was more symbolic, which I really liked.
Considering all these elements, my suggestion for re-working the poem would therefore be something like this:
Split the darkness on the floor of mirrors
on which the soul broke the Crystal of lucky beliefs.
When the crazy dancing of the tree offers the child
the music of the sky
every night.
Those are a cry of hope and the future seeing.
The syllabic pattern would thus shift from 12-11-20-12 to 10-13-13-6-3-12, which makes the increase of verse length in the middle more gradual.
Once again, I'm only nitpicking -- and the reason I took the time to do this is because I think your poem has potential. Hoping some of this will be of use to you, read you soon!