Violet Crumble – 10 and 20mm Sounds good enough to eat. Purple & white in colour. Mahogany Swirl 10 & 20mm Beautiful dark reds with splashes of creamy greys. Tumbled Biscuit – 20 – 40mm Creamy rock with swirls of caramel & mocha. Natural Gravel – 5mm Small pebble. Great for fish tanks.