Abstract: The invention concerns a watch crystal (1) made of hard mineral material, in particular a crystalline material such as corundum, sapphire or spinel, including a non-circular optical lens (4) shaped in the thickness of the material of the crystal. The lens is formed by machining and polishing a recess (5) preferably situated in the lower face (3) of the crystal. Its contour can have reentering angles, and can be for example rectangular. The machining is effected by means of a brush which hits the bottom of the recess with the addition of a polishing medium.

Abstract: A watch case has a water-tight casing (1) capable of being manufactured economically in hard materials, the casing parts being held assembled by an external support device (2) having structure for attaching the-case to a wristlet or other fixing apparatus. The casing (1) is formed of stacked parts preferably including a crystal (7), an annular middle part (9) and a back cover (8). The mutual contact surfaces (13, 14, 15, 17) of these parts are polished and have no sealing gasket. The support device includes two parallel metal clamps (25) in the form of an open or closed frame, having two portions assembled by screws (28) arranged axially to grip the casing in the clamp. The casing (1) may be made entirely of sapphire, but other materials having zero porosity or a closed structure such as hard metals, ceramics or mineral glass may be used.