Symplectite

A symplectite (or symplektite) is a material texture: a micrometre-scale or submicrometre-scale intergrowth of two or more crystals.

Symplectites form from the breakdown of unstable phases, and may be composed of minerals, ceramics, or metals.

Fundamentally, their formation is the result of slow grain-boundary diffusion relative to interface propagation rate.

[1][2][3] If a material undergoes a change in temperature, pressure or other physical conditions (e.g., fluid composition or activity), one or more phases may be rendered unstable and recrystallize to more stable constituents.

The intergrown phases may be planar or rodlike, depending on the volume proportions of the phases, their interfacial free energies, the rate of reaction, the Gibbs free energy change, and the degree of recrystallization.