Where can I find the list of 'autoreplaceable' iOS special characters?

Question

Several special characters (⬇, for example) when being used in labels, etc are replaced with images automatically.

Where can I find the complete list of such replacements?

Thanks in advance

UPDATE: I know that I can simply copy-paste a lot of special characters to define what are the magic ones but I am interesting whether this magic is documented anywhere?

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PROOF:

Source:

UILabel *lbl = [[[UILabel alloc] initWithFrame:CGRectMake(50, 200, 220, 25)] autorelease];
lbl.text = @"Did you see that? ⬇";
[self.view addSubview:lbl];

Result:

Answer 1

As far as I can tell, the "image" is actually an emoji icon. The iphone uses softbanks emoji encoding ranges, so here is the list of those emoji icons and their respective codes.

Also see this question on how to put those charcodes into use.