I have an opportunity to purchase a large quantity of tufa rock from a farm field. Very economical and lighter than other rock material. I plan to redesign my front yard with raised beds for my conifer addiction, I mean, collection :) . My understanding is that tufa is alkaline based and conifers tend to like acid bases. I am wondering if there is a down side to using tufa as the border ? I would fill in with a sand based /compost soil mix. I am sure there would be some leaching from the tufa but not sure if this would be a deal breaker for my conifers. My soil is clay-based, so that is why I make raised beds for my conifers.