Negative crystal combinations (and a ? about obsidian)

Are there certain crystals that should not be used together? Like, a crystal that dampens or hinders the other crystal's effectiveness.

I just bought a black obsidian stone yesterday, and when I hold it in my palm for any more than 1 minute, my palm actually gets uncomfortable, it's almost spasm-y. I've cleansed the obsidian in white sage smoke, but it seems to burn my hand. Is this bad? Or am I just painfully sensitive to the obsidian's energy?

[Selbor13]

Maybe you are tapping into its essence or just sensitive to it, after all obsidian was created by volcanic activity. Have you ever felt moldavite? now that packs a punch!

As far as combinations, it really depends on you. Some crystal amplify the energy of other crystals, some balance each other out. In my experience I have not had any negative effects with combinations. Just remember that crystals help clean and clear out junk, many times that's what you will feel, some people might interpret that as a bad thing or negativity. To me it's just the effects of the cleansing and the releasing of junk out of your system.