Although a rather usual mineral throughout much of Western Ohio, Calcite geodes are a highly uncommon occurrence. Unlike many midwestern states where Quartz geodes are widespread and abundant, geodes of any type are a rare find throughout the state. The Calcite in these geodized brachiopods formed in two or more generations. The first generation of Calcite forms a coating of drusy appearing crystals completely lining the hollow interior of the fossil. While rare doubly terminated crystals are occasionally found, most first generation Calcite crystals are well formed clear white to grayish brown, singly terminated scalenohedrons or scalenohedrons with rhombohedral modifications. Typically, first generation crystals areRead More →

Although one of the less common habits of ferroan dolomite found at the Lamereaux road bridge locality, multiple-growth hillocks do occur with some frequency throughout the septaria. This habit has been illustrated by crystal 1 in figure II. This type of growth is not linked to any particular generation, but has been observed more frequently in the 2nd, 3rd and 4th generations. The reason for the hillocks is not completely clear, but they do appear to grow simultaneously with the central crystals. In general, the hillocks are crude in comparison to the central crystal, but are of identical form, color and luster. The number ofRead More →

Next Page »