Different custom footnote symbol on the same page

I have redefined the footnote symbol in the preamble as follows:

renewcommand{thefootnote}{color{black}$spadesuit$}
newcommand{txtn}{textnormal}

Now I have some text, a footnote, and then some more text where I want another footnote, but I want a different symbol (so the reader knows which footnote I’m referring to). How do I redefine the footnote symbol without redefining it globally?

[(x^a)^{-1} = (underbrace{x cdot x cdot ldots cdot x}_{a txtn{ terms}})^{-1} = footnote{tiny By exercise 15.} (x^{-1} cdot x^{-1} cdot ldots cdot x^{-1})^a = footnote{different symbol for this footnote} x^{-a}.]

I expect there to be some kind of command such as footnote[symbol]{footnote}.