Australian Noble Opal

Australian Noble Opal
 Size: 9cm by 4.5cm by 2.5cm for 130gr
 
 Wikipedia definition:
 An opal is a mineral composed of hydrated silica with the formula SiO2 · n H2O, with traces of uranium, magnesium, calcium, aluminum, iron, arsenic, sodium and potassium. The water content is usually between 3 and 9  %  ; it can reach 20  % depending on the variety.