Many of the opals mined in Ethiopia, especially from the Welo deposits, are hydrophane opals. "Hydrophane" is a name used for a porous opal that has the ability to absorb water. A change in color or transparency often accompanies the water absorption.

How can you tell an opal from a Hydrophane?

After a few seconds of allowing the water to either evaporate or soak into the stone, reexamine the appearance. If the water is absorbed into the stone, that area's refractive index will be slightly different, creating an optical aberration where the drop is placed and confirming that the stone is hydrophane.

How do you care for a Hydrophane opal?

The nature of hydrophane opals means that absorbing water can enhance their fragile qualities. Avoid prolonged immersion in water. If stones absorb water, let them dry thoroughly before wearing. Depending on how much, they can take up to a week to dry.