Sandstone

I am presently opening up a quarry containing deposits of sand (http://maplered.com) Stone (http://g603.net) (Table Mountain Sand (http://maplered.com) Stone (http://g603.net) ) in the Western Cape province of South Africa (nearest city Cape Town). The deposits, (evaluated from surface sampling, as core sampling is cost prohibitive at this stage) have a wide range of colour from deep red to pink to almond to cream to white. The coarseness/hardness ranges from crumbly soft to a fine grain and (http://maplered.com) relatively hard.
I need to know whether a surface sampling is indicative of what lies beneath with particular referance to colour and (http://maplered.com) hardness.
Anybody?