Chromium-Caesium Alum
Difficalty: 1/5
Chemical Composition:
CsCr(SO₄)₂ * 12H₂OChromium–caesium alum is a striking member of the alum family, known for its saturated coloration and well-defined geometric crystals. In its pure form, this compound typically crystallizes as a black octahedron with triangular sliced edges. The presence of chromium(III) gives the crystals their characteristic deep violet hue, which intensifies as the crystal grows. Under bright light, the color shifts between warm magenta and cooler bluish tones depending on the viewing angle.
When mixed with other caesium alums—such as iron–caesium alums—the color can vary notably. Mixed crystals often display gentle gradients rather than uniform pigmentation: pale lavender toward the edges and deep violet toward the core.
Chromium–caesium alums tend to grow slowly but cleanly in solution, forming unique octahedra with triangular sliced edges. When grown with care, without non-alum impurities or significant temperature fluctuations, they can achieve gemstone-like brilliance that makes them particularly appealing to collectors and crystal growers.
When mixed with other caesium alums—such as iron–caesium alums—the color can vary notably. Mixed crystals often display gentle gradients rather than uniform pigmentation: pale lavender toward the edges and deep violet toward the core.
Chromium–caesium alums tend to grow slowly but cleanly in solution, forming unique octahedra with triangular sliced edges. When grown with care, without non-alum impurities or significant temperature fluctuations, they can achieve gemstone-like brilliance that makes them particularly appealing to collectors and crystal growers.
Known Crystal Shapes
Gallery
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