A cathedral with a thick agate band, a layer of quartz inside it, and purple only in the druzy at the surface.
That order is the whole history of the cavity, readable from the outside in. Silica arrived first and built the agate. Quartz grew next, clear, because there was no iron in the water at that point. Iron only turned up at the very end, which is why just the final skin of tiny crystals came out amethyst.
The back and base are cemented and the outside painted dark, standard for cut geodes. The crystal itself is untouched.
Mineral: Amethyst, the purple variety of quartz (SiO₂)
Crystal system: Trigonal
Origin: Brazil
Hardness: 7 on the Mohs scale; hard, though individual crystal tips chip easily
Treatment: None to the amethyst. Backing, base and exterior are cemented and painted, standard practice for cut geodes
Dimensions: 23 x 10.5 x 30.5 cm
Weight: 11.65 kg Note: Keep it out of direct sunlight. Sustained UV breaks down the iron centres that produce the purple, and amethyst that fades does not come back
You will receive the exact piece photographed.