Almost looks like either honey or copal

Lovely work, but as solkee says, you can't add text in Photoshop, however there is nothing against writing it on the paper. If your handwriting isn't as good as in the photo. Print the text and then put the stone on the paper and re-take the photo

A matter of choice! Have a heart of stone if you wish, but then don't go swimming

The text can't be added in PS, that is against the Rules & Guidelines. I would advise you to edit your entry before it gets pulled by the moderator. To edit your entry go to My Stuff> My Contest Entries> Edit Entry.

In my language have a heart of stone is to be a cold, hard and insensitive person . I suppose it is so also in the language of the author

What does a "heart of stone" means?

simple and elegant, bravo