Classification and selection of crystalline object

PURPOSE: To surely, precisely and quickly classify and select a crystalline object according to shape by forming the image of the crystalline object seen from a certain determined angle, and comparing the image with a preliminarily selected template. CONSTITUTION: A crystal 10 is placed on a transparent or translucent surface 50, and the diffused light reflected by a diffuse reflecting plate 30 is projected from the back side. At that time, the translucent crystal can show the outside profile and inside profile. Since the object to be intended is formed of a crystal of cubic system, and the orientation of crystal is limited, the formed image can be classified by being compared with a limited number of templates. The comparing means is formed of a computer, and after the image is converted into a digital signal by the computer, the digitized image is mathematically compared with one or more templates. The template observed to be sufficiently and satisfactorily conformed to the image is moved to change the geometric parameter.