This card is likely the fusion of "Gem-Knight Crystal" and "Gem-Knight Iolite". The origin of the word iolite is violet (the same color as amethyst). Both "Iolite" and "Amethyst" wear a ring on their helm and wear an armored skirt. The weapon and shield that "Amethyst" uses are the same color as "Gem-Knight Iolite".
The chemical structure of iolite contains iron and magnesium. Both elements are said to contribute to the violet shade of amethyst.