Answer:
Place a filter funnel on the top of a conical flask.
Roll the filter paper into a cone and place it on the flask.
Pour the mixture of sand and water into the conical flask with the filter funnel and paper.
Wait till all the sand is left over in the filter paper and all the water has been separated.
(You could also heat the sand in a warm oven to remove any water remaining)
The younger rock would be black and have like no stains and it would not be as dirty as the older rock hope this helps!!1