CALCITE (var. “CLAMSHELL”)

HISTORY, NAME, LOCALITIES:  “Clamshell” calcite is a recently discovered mineral-fossil composite.  Its name alludes to the replacement of portions of fossilized clamshells by calcite crystals.  It is known to exist only at a single locality at Fort Drum, Florida.

MINERALOGY, PROPERTIES, OCCURRENCE: Calcite [calcium carbonate, CaCO₃], pronounced CHAL-site, is the most abundant carbonate mineral.  It crystallizes in the hexagonal system (trigonal subsystem); crystals are usually rhombohedral, scalenohedral, or prismatic with an unusually wide variety of habits.  It has a Mohs hardness of 3.0, perfect cleavage in three directions to form rhombohedrons, vitreous-to-dull luster, and a specific gravity of 2.7-3.0.  It is often white or colorless, but impurities create a wide range of pale colors.  Calcite develops in many mineralogical environments including, in the case of “clamshell” calcite, sedimentary rocks.  In the “clamshell” variety, calcite has replaced parts of the fossilized shells of Mercenaria permagna clams within a limestone matrix.  The calcite occurs as well-developed, transparent, “dogtooth” crystals with a golden color that is caused by the presence of iron.  “Clamshell” calcite mineral-fossil composites range between one and four million years in age.  Specimens are dug by hand from a limestone pit that has now been flooded and is closed to further collecting.

METAPHYSICAL PROPERTIES, LORE, USES: According to metaphysical practitioners, calcite enhances learning abilities, reduces fear and stress, removes negative energies, and promotes creativity and imagination.  “Clamshell” calcite has not been assigned any specific metaphysical significance.

COLLECTORS’ INFORMATION: “Clamshell” calcite is collected for its attractive crystals, unusual occurrence as a mineral-fossil composite, and rarity.