Here is a link related to Creating a database snapshot.

http://msdn.microsoft.com/en-us/library/ms175876(v=sql.105).aspx

You can go ahead a create a snapshot based on the Mirrored Database that you have (in Synchronized state). There are other things to consider in a snapshot, like how sparse files are used, the space usage as presented on the explorer vs. the actual disk usage.

basic syntax:

CREATE DATABASE <DatabaseSnapshotName>

(NAME = '<Logical Data File Name>', FILENAME = '<Valid Snapshot Full path and filename>')

AS SNAPSHOT OF <Databasename>;

For a Database called DB1:

CREATE DATABASE DB1_SS1

(NAME = 'DB1', FILENAME = 'E:\MSSQL\Snapshot\DB1_Snapshot.SS1')

AS SNAPSHOT OF DB1;

And then you can go ahead and issue :

USE DB1_SS1

GO

SELECT ..... your queries...