Calcite with Siderite

This locality is a bit obscure but is known to Colorado collectors as it has produced some of the most interesting and easily identifiable Calcites from anywhere in the state. These Calcite crystals occur in septarian nodules found in the Mancos shale formation. As far as I know there are only three reported minerals from the locality – all carbonates, i.e., Calcite, Siderite and Dolomite. In the early 1980s, my father collected several superb specimens from this locality, which he referred to as "Windy Ridge", but the correct name for the locality is Billy Creek. The piece hosts dozens of excellent, sharp, gemmy/translucent, well-formed, classic, colorless to white rhombohedra, with a gorgeous satiny interior. The crystals are associated with tan/pink botryoidal Siderite and are sitting on a contrasting gemmy brown scalenohedral Calcite on matrix. The largest Calcite crystal measures 1.1 cm, and almost all of them are virtually damage free. A very attractive and hard to find display specimen that would make a great addition to a Calcite suite or a collection of Colorado minerals. Specimen# CO712B89