Pumice is available here as well and is widely used by hobbyists and commercial growers. Here the 3/8”-minus is unwashed and contains fines. The 5/16” size is sold clean. There is also a larger size. I know commercial growers in Tucson who swear by including fines in their soil mixes and who say they do so because it improves the soil texture significantly. The color of our local pumice is off white. Here is the link: http://www.tufflitelightweightpumice.com/index.htm I’ve used all three of these sizes interchangeably in pots, vegetable/herb garden beds, seed and bulb mixes. I have no experience with fines settling to bottoms of pots, Rodger, and your comment makes me wonder how and how much pumice varies by quarry. Anyone know? Best, Pam Pamela Slate P.O. Box 5316 Carefree AZ 85377