Opal has the same chemical composition as quartz (silicon dioxide but also contains 1 to 2 percent water and is not crystallised

Common Opal, doesn't have the play of internal colours that precious opal does,  it is translucent with a palette of colours including honey, orange, blue, green and red. Common opal also appears with dendritic inclusions. 

These opals include opal fossil wood, which is caused by the replacement of the organic material in wood with opal and Hyalite a colourless glass-clear opal sometimes called Muller's Glass or Water Opal, Jelly Opal and Chrysopal.

Opal is a delicate stone with a fine vibration. It enhances cosmic consciousness and induces psychic and mystical visions. Opal stimulates originality and dynamic creativity, it helps in accessing and expressing your true self. Opal is absorbent and reflective. It picks up thoughts and feelings, amplifies them and then sends them back.


https://www.healingwithcrystals.net.au/opal.html