Artificial Sapphire: Stone or Glass?


I’m a maker wanting to create a seder dining service acceptable to everyone. Ashkenazi rabbis, the strictest, consider glass to be non kasherable for dining ware.
A technique has been devised by hobbyists to inexpensively create artificial sapphire, chemically known as corundum, from aluminum oxide powder with elements for coloring, using a microwave oven for fusing. This now makes sapphire accessible as an art material even if not gem grade. It can melt at several thousand degrees when growing lab-created gemstone or laser crystals. The microwave oven emulates this process for small quantities and brief moments. Sapphire can only be worked with diamond abrasives.

Glass is in the general class of silicon based materials, adding either sodium for common glass or boron for Pyrex. Glass melts about 800 Fahrenheit. Hence sapphire differs chemically from glass. Glass can be molded or blown.

For additional reference, porcelain, which is also non kasherable, is based on kaolin, which is mined from river banks typically, and fires at about 2000 Fahrenheit into a glasslike substance.
I am hoping artificial sapphire would be better than glass or porcelain for kashering since natural sapphire is considered stone by the rabbis. Mere glass is considered permeable here.
Thank you for considering this question.



  1. Gosh, what a wonderfully detailed question! Unfortunately, I do not have the expertise to answer it. Personally, I think that your question would be best addressed to either the OU or the Star-K organization, as their Kashrus experts are able to answer all kinds of questions that deal with the Kashrus of utensils and their composition.

    The OU can be contacted through their email:
    The Star-K can be contacted through their site:

    I wish you every success in your endeavors!

    Best wishes from the Team