| 摘要 |
<p>Apparatus for gem lapidation comprises a curved abrasive surface (S2) and a faceter (A-C). The abrasive surface (S2) is rotatable relatively to the faceter. The faceter is mounted at two points (A, B) on another spherical surface (S1) such that in use when a gem is held by a gem- carrying terminal (C) of the faceter against the abrasive surface (S2) subsequent movement of the faceter relatively to the abrasive surface causes the gem to move along a path having substantially the same radius of curvature as the abrasive surface whereby a constant angle is maintained between the gem carrying terminal and the normal at the point of contact of the gem with the abrasive surface (52). Gemstones having at least some spherical facets (convex or concave) may be so made. <IMAGE></p> |
