Try Opalina or Opaline if you don't like Opal. There have even been a few Opalinska's.
Pronunciation: OH-pull, OH-pall
Potential nicknames: Opie, Palla, Ollie
Origin: Hindi and Sanskrit (from the word upala), meaning "gem, precious stone." From Sanskrit upala came the Greek word opallios, and then Latin opalus. Some say the name Opal came from the wife of the god Saturn, who was named Ops. The term/festival Opalia refers to her, just as Saturnalia refers to Saturn. Opaline and Opalina are longer versions of the female name.
Popularity: Opal was last on the Social Security Administration's top 1000 list in 1960, at #920, after a very successful run from the early 1900's. It made it to #81 in 1911. In 2010 there were only 80 baby girls named Opal. In 2011 there were 92 girls named Opal. There were no baby girls named Opaline or Opalina.
Fun Fact: (1) The opal gemstone comes in a wide variety of iridescent colors, mainly with a milky white background. Most Opals come from the Australian outback, and there is a legend there that claims "The Creator" came down to Earth upon a rainbow to send a message of peace, and where his foot touched ground, the stones became opals. (2) Pliny the Elder, from Roman times, said the opal contained the best qualities of all other gemstone colors.