Nephrite is one of only two minerals properly called jade, and the gourd is one of its oldest decorative forms in China. Because nephrite is exceptionally tough — an interlocking fibrous structure — a thin-walled carving like this holds up rather than snapping.
It is worked entirely by abrasion: rough blocks are cut, then ground against rotating wheels with progressively finer grit until the form emerges. Colour varies from near-white to a grey-green, and natural inclusions run through every piece. Keep it from swinging into the glass.