Spiral growth pattern in a Vietnamese pink sapphire.

Occasionally, we find a gem inclusion that uncovers the crystal structure and growth pattern of the host gem. These spirals start at an inhomogeneity in the lattice, such as an enclosed crystal or twinning plane. Each twist in the spiral records another stage of growth in the crystal, revealing the pattern in which the atoms organised themselves during crystallisation.

The veils forming the spirals consist of fluid inclusions. These droplets of metamorphic liquids contain samples of the mother ichor from which the gem precipitated, and record the ambient formation conditions. When analysed they allow an estimation of pressure/temperature conditions giving us  an increased understanding of the geological events responsible. In this case, the pulse of mineral transformation was linked to the Himalayan orogeny.

Loz Image of sapphire from Luc Yen, Yen Bai province, Vietnam.

Image credit: Loz