Looks like a variety of "white onyx" a.k.a. chalcedony. it's very common in Mexico, where the Mexican tourist industry carves onxy (the usual honey-colored onyx) and "white onyx" into chessmen, animal shapes, bowls, and geometric forms, like yours. In addition to other characteristics, such as the banding visible in the one on the left of your photo, the light-reflection showing a "waxy finish" look (instead of a glossy-smooth finish) on the one at the right makes me think it is "white onyx."