Decorative River Rock Per tonne: $88 Per 30L bag (55 pound): $7.99 Decorative River Rock is a mixture of white, grey, red and black granite that is sourced in Ontario. Adding river rock to your garden can create a dramatic yet natural look. River rock is an attractive, versatile, low maintenance addition to any property and can be used for garden edging, pathways, rock gardens, lawn edging, container plant toppings, and more! The two sizes we carry are 1″ – 2″ river rock or 2″ – 6″ river rock. Bag-your-own 2-6″ river rock for $10/bag.