Abstract: A jewelling and ornamental material comprising many amorphous silica spheres regularly arranged in a three-dimensional array and a zirconium compound filled in pores existing among the amorphous silica spheres, the amount of the zirconium compound being 0.005 to 8% by weight, as zirconium, based on the entire material; and a process for its production. This material has a play of colors inherent to natural opal, and excellent durability.

Abstract: A jewelling and ornamental material comprising many amorphous silica spheres regularly arranged in a three-dimensional array and a zirconium compound filled in pores existing among the amorphous silica spheres, the amount of the zirconium compound being 0.005 to 8% by weight, as zirconium, based on the entire material; and a process for its production. This material has a play of colors inherent to natural opal, and excellent durability.

Abstract: A variable venturi type carburetor is provided having a vacuum generated in the venturi portion in accordance with the throttle valve opening. The vacuum is transmitted into a suction chamber through a vacuum passage so as to balance the force which is the sum of the force exerted by a suction spring and the force exerted by the atmospheric pressure introduced from an atmospheric pressure chamber. The suction piston is set to provide a cross-sectional area of the venturi portion corresponding to the intake air flow rate. The suction piston is provided with a guide groove receiving a guide roller which is rotatably mounted on a guide pin provided on the carburetor casing to oppose to the guide groove. The guide roller is adapted to roll along the guide groove to smooth the movement of the suction piston and prevents the suction piston from being rotated.