Answer:
The opal is the National Gemstone of Australia. The opal is almost exclusively located within Cretaceous sedimentary rocks of the Great Artesian Basin, Intense weathering resulted in extensive silicification at relatively shallow levels within the Tertiary regolith.
All of these are the causes that led to the Russian Revolution. The Russian Revolution consists of two revolutions actually and those are the February Revolution and the October Revolution. The Russian Revolution led to the end of Tsarists autocracy and led to the rise of the Soviet Union.
