102-03 Cactus Berry Sand and gravel.
This tan areas on your model railroad layout.
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. These organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Other carbonate grains composing limestone’s are ooids, peloids, intraclasts, and extraclasts. We crush it down to make 102 Kaibab Limestone Ballast.