YELLOW OPAL - is NOT a precious OPAL but belongs to the much larger group of so-called common OPALS.
ALL OPALS are amorphous and not crystalline. However, the common OPALS lack the famous "opalescence", i.e. the play of colors. Nevertheless, many of the "normal" OPALS are also cut into jewelry.
The common OPALS include, for example
MOOSOPAL, HOLZOPAL, LEBEROPAL, KASCHOLONG OPAL = PORCELAIN OPAL HONIGOPAL....u.a.
Weight of this raw OPALS from Pireska in Madagascar
450 g Dimensions: 10 x8 x 8 cm