The approximate value in US$ of the world silver market capitalization is 1.285 trillion US$.
This calculation has been made estimating the total amount of silver mined so far, which is 1.74 million metric tonnes. The current price of silver is 20.94 US$/ounce and there are 35274 ounces in a metric tonne.
Here is a chart that shows the total silver extraction since the year 1900:
Source of the chart
For further information, read this article