Apr 22
Aquamarine is the pale blue-green variety of beryl (Be₃Al₂Si₆O₁₈), and it grows in hexagonal prisms thanks to beryl's ring-silicate structure — six silica tetrahedra linked in a ring, stacked like a column of donuts. The blue comes from tiny amounts of iron in the Fe²⁺ oxidation state; heating shifts it to Fe³⁺, which is why some market aquamarine is actually heat-treated greenish beryl. This specimen is from Xuebaoding in Sichuan, a high-altitude pegmatite locality famous for combining aquamarine with scheelite, cassiterite, and these pearly mica sheets in a single specimen — a combination you almost never see anywhere else.
