Posted: Yesterday at 14:30
Loved this bit - "Please note that due to high regional delivery surcharges imposed by the haulage company we are unable to deliver this item to Cornwall, Highlands, Moray or Aberdeenshire using our free delivery service."
So what exactly is Highland Grey stone then . I guess they only mean the colour.
Looks like it is a form of limestone. Found this on the web which seems sensible advice
Limestone, too, is commonly found as rocks of waterfalls and pond edges (but these rocks are not particularly flat unless very large or cut that way), and as decorative elements when large examples are positioned in or near the pond (the irregular, weathered field stones). Some limestone varieties (the massive limestones) will hold up quite well while sitting in water (and will actually help buffer acid contributors to the pond – keeping the pH between 7.0 and 8.5); whereas, other varieties (the crumbly limestones) will leach lime into the pond and will increase the alkalinity of the water. An alkaline pH of greater than 9.0 will spell doom for fish; needing the removal of sources of alkalinity or chemical correction. (With regard to high pHs, any concrete, concrete blocks, and mortar used in the construction of a pond should be treated with lime neutralizers or a non-toxic sealant to avoid leaching lime into the water.) A close cousin to limestone is dolostone (formed of the mineral dolomite). This particular rock form of calcium carbonate will not likely increase the water’s pH. Within our pond, dolostone blocks are used in the walls that form several sides of the pond, sticking out above the water level and extending to the bottom.