|A native cut stone that was designed to show off the dendritic inclusions and not cut for light return. The "dendrite" are a metal oxide crystallization along a crack or thin seam in the quartz crystal. They are nearly flat and planer. The likely candidate is manganese oxide dendrites. Dendrites often form along surfaces or in thin cracks. The pattern can be caused by their crystallization from an evaporating solution, or their replacement of a soluble metal with a different oxidation potential.
Close ups are shown directly below. Even further below are two pictures of dendrites forming on the surface of a vein of granular milky quartz. The dendrites likely formed in a thin seam in the vein, and the sample probably broke along this weakness when collected, bringing the dendrites into view.