The term 'birthstone for some Scorpios' can refer to two different gemstones: OPAL (4 letters) and TOPAZ (5 letters). OPAL is a hydrated amorphous form of silica, which is composed of silicon dioxide and water. It is known for its unique play of color, which is caused by the diffraction of light passing through its microstructure. TOPAZ is a silicate mineral that is typically found in igneous rocks. It is known for its hardness and its wide range of colors, from yellow to blue.