Is a fissure filled ruby real?

Answer 1

The rubies used to create fissure-filled stones are generally of very low quality. This kind of ruby is usually made more porous with an acid treatment. Then it is heated with other materials that make glass when the ruby gets hot enough. The glass fills in pits in the ruby. Therefore, parts of the stone are ruby, but parts are actually glass. Whether you consider this ruby "real" is up to you since parts are ruby, but depending on the size of the fissures that are filled, a significant part of the stone can be glass. The stones can be pretty, but glass does not have the same properties or hardness of a ruby.