Strontianite, a carbonate closely related to Celestine, is one of the more intriguing micro minerals found at Georgetown. The presence of Strontianite at this locality is most certainly related to the on going weathering process of Celestine. As the Celestine is broken down, the Strontium forms small snow white radiating sprays of the carbonate.
As a rule, Ohio Strontianite forms tiny, orthorhombic, needle-like spires with curved tips, typically in bundles, sheaves, or ball-like sprays. These curved tips are typically only noticeable under 15x magnification or greater. At first glance, these sprays appear to be quite typical of Ohio Strontianite. However, a quite unusual occurrence for Ohio Strontianite has been recognized in geodized brachiopods from Georgetown.
Upon close inspection of Strontianite clusters from this locality, one can easily observe that many of these radiating sprays are comprised of both Strontianite and Celestine crystals. The Celestine is identified by bladed crystals with flattened or truncated terminations. This crystal form is generally never employed by Strontianite.
Approximately fifty percent of the Strontianite sprays found in geodized brachiopods from the Georgetown area are intergrown with Celestine in this manner. The photo to the upper right exhibits one of these larger sprays intergrown with Celestine. A careful eye can discern both minerals in the photo. The dark mass embedded in this Strontianite cluster is a sulfide, likely either Pyrite or Marcasite.
Although the typical Strontianite cluster measures no more than 1/16 inch, single Strontianite sprays have been recovered up to 1/4 inch. Strontianite at this locality, tend to form in one of three identifiable habits. The first and most common habit is a single radiating spray or “ball” cluster. The specimen pictured in the upper right photo, although intergrown with Celestine, is an example of this habit.
The second two habits are more closely related. Often, smaller and less developed sprays will resemble a bow tie. These “bow tie” clusters appear to develop two sprays in opposite directions. The photo to the lower right is a classic example of this development. As this type of cluster matures, it often forms two connected ball-like clusters of equal size. This “double ball” habit is displayed in the photo to the left.