Pink tourmaline was on-trend around the turn of the century (when the first Oz books were written).

“Much of the demand for pink tourmaline was the result of the obsession on Tzu Hsi, the empress dowager of China who became enamored with tourmaline from San Diego County in 1901. Before her death in 1908 — she was buried in gems and laid to rest on a tourmaline pillow — she imported huge amounts of it.” –San Diego Union Tribune

Close, but not quite. Glinda compelled the witch Mombi to reverse her spell which had concealed Ozma as the boy Tip years before. I believe it said something like Glinda as a sorceress didn’t want to sully herself with witchcraft.

but this is about osma of oz, right? So her lips probably *were* green

I’d completely forgotten about this until now, but you’ve reminded me that there’s such a thing as a “watermelon tourmaline,” and it looks exactly how you would anticipate.