Patents Assigned to Astrid Corporation, Limited
  • Altering the appearance of corundum crystals
    Patent number: 4039726
    Abstract: The appearance of a corundum crystal is altered by subjecting the crystal to an elevated temperature while maintaining the crystal in contact with a powder comprising a major amount of alumina and a minor amount of a metal oxide colorant.
    Type: Grant
    Filed: March 8, 1976
    Date of Patent: August 2, 1977
    Assignee: Astrid Corporation, Limited
    Inventors: Ronald Ray Carr, Stephen Dale Nisevich
  • Altering the appearance of corundum crystals
    Patent number: 3950596
    Abstract: A corundum crystal whose surface is altered by contact with a powdered metal oxide colorant at an elevated temperature within the range of 1600.degree.C to a temperature below the fusion temperature of the said powder, said metal oxide colorant consisting essentially of an oxide of titanium and at least one metal oxide selected from the group consisting of iron, chromium, vanadium and nickel, said metal oxide colorant being sufficient to impart color to the surface of the crystal.
    Type: Grant
    Filed: May 8, 1974
    Date of Patent: April 13, 1976
    Assignee: Astrid Corporation, Limited
    Inventors: Ronald Ray Carr, Stephen Dale Nisevich