Polished slab of bowenite serpentine, a variety of antigorite. Bowenite is a hard, compact variety of the serpentinite species antigorite (Mg 3 (OH)O 4 Si 2 O 5). [1] Classed as a semi-precious gemstone, [2] it has been used for tools, weapons and jewellery by the Māori in New Zealand, [3] [4] and for jewellery by Fabergé. [5]