check the pillars at the end of Melville Drive.
From that diagram, the most weathered stones appear to be inferior quality Gatelawbridge red sandstones. No Craigleith sandstone in them?
I think one of Cockburn's points, which they should make more of, is that St. James Square and the surrounding tenements were all of Craigleith Sandstone and pulled down and were replaced by the concrete behemoth of the St. James Centre, St. James Thistle Hotel and New St. Andrews House which stuck out like an ugly sore thumb. Portrait gallery aside, most of the buildings around there are sandstone. If you stick a spanking big new limestone and glass, or metal and glass, shopping centre in there it's going to be every bit as conspicuous as the wrong the developers are claiming they are trying to right, and given time will look every bit as out of place and ugly. The council should be in a position to demand top-quality and fitting cladding for such a huge, prestigious development surrounded by the (Craigleith Sandstone) world heritage site.
Maybe they should just build it out of Lego?
Perhaps the Cockburn would like to add wheels to the nearby portrait gallery and trundle it away to Dunbar WHERE IT BELONGS, the horrid red interloper.
I believe it belongs with its redstone kin in Dumfriesshire (it was built in the time of railways, unlike the New Town, so they had the luxury of shipping in such fancy "foreign" stones.