A mounting (10) holds a grooved gemstone invisibly to a setting. One end of the mounting (10) has arms or extensions (14), reinforced by struts (26), to receive the gemstone and protrusions (16) extending inwardly from the arms (14) to fit in the grooves of the gemstone, the mounting (10) further comprising a retainer which is inserted into the setting, and then twisted to retain the mounting (10) in place and may lever the arms (14) to press harder into the groove. The mounting (10) is adjustable. The retainer may be cylindrical, with a lengthwise split (28) to make the deformation easier. As an alternative, the insertion may comprise planar members (42, 44; 52, 54; 62, 64; 72, 74) which are likewise inserted and then distorted. The mounting (10) may have two or more gemstone compartments. Multiple coronets (94) may be fitted on a molded base (92) with reinforcements (102) between the coronets.