The term 'whitish birthstone' refers to the gemstone OPAL, which is a 4-letter word. OPAL is a hydrated amorphous form of silica, which is composed of submicroscopic silica spheres that are arranged in a regular pattern. It is an opaque stone with a waxy luster and can range in color from white to black, with flashes of yellow, orange, green, red, and blue. It is the traditional birthstone for October.