Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/160

 precious opal is not quite so hard as rock crystal; it is frequently full of flaws, which greatly contributes to its beauty, as the vivid iridescent colors which it displays are occasioned by the reflection and refraction of light, which is decomposed at these fissures, It is never cut in facets, but always hemispherical. It is generally small, rarely so large as an almond or hazel nut, though I have seen some specimens the size of a small walnut, for which several hundred pounds were demanded. At present,a pretty opal may be bought at from one to three, or five guineas, sufficiently large for a pin, or ring stone. It requires great care and judgment in the cutting, as it is fragile, and easily spoiled,

opal in all ages has been highly esteemed; the history of the Roman senator, who preferred death rather than give up his opal ring to the emperor Nero, is familiar to