SSWUP ISL - Build

[nachoman]

Its not Quartz... Its Dolorite, common in South Africa and used in most concrete and road surfacing... It does not look so great in those photos, colour is darker in real life... Here are a couple more to judge on... ]

Dolerite is a volcanic rock, and Dolemite is a carbonate rock.

Either way, I don't often see rounded rocks used as ballast in the USA. Mehanically crushed rock seems more common. From a modeling standpoint, color, texture, and size should be all that matter. Ballast is something I think looks better slightly larger than scale size. I also think it looks better if the color is not uniform. That often means mixing two sizes and colors of the Woodland Scenics commercial ballast, or going with a natural product. What you have done to your layout looks good.