Gomed or Hessonite is one of the Nava Ratn (nine gems).
It is for Raahu, but it's not so easy to understand the identity of Gomed from ancient perspective. Since Vaidik times Gomed meant garnet, even orange garnets were also called Gomed (Go+med = cow's urine). The ancients did not know the difference between garnet (hessonite) and garnet (spessartite), because both were simply Gomed.

In Thailand also Gomed simply means garnet, in particular the orange one. So with Gomed we have the choice of hessonite or spessartite garnet. Either one is the same energy of Raahu. They both cost the same, although the Spessartite is more rare.