West Virginia State Gemstone
Lithostrotionella is technically not a gemstone, but fossilized coral from the Mississippian Period. This prehistoric coral is a member of the order Rugosa, also called the Tetracoralla. The order is namedRugosa due to the wrinkled, or rugose, walls of these corals. This extinct order of coral was abundant in seas of the Middle Ordovician to Late Permian periods, some 255 to 475 million years ago.
Lithostrotionella occurs in various colors due to the impurities in the minerals present during formation. In West Virginia, lithostrotionella comes in several colors, including light to dark blue-gray, pink, and red.
Lithostrotionella is found in the important geological area called Hillsdale Limestone, in what is now part of Greenbrier and Pocahontas Counties, West Virginia. The state legislature designated this fossil its official gemstone on March 10, 1990.
This genus was named by its founders, Yabe and Hayasaka, in 1915.
FORMATION AND OCCURRENCE
About 340 million years ago, ground water deposited dissolved silica into decaying coral that had previously lived in seas that once covered the land. The silica filled the cavities in the coral, and the coral reefs hardened into fossilized coral, which is a variety of chalcedony. Chalcedony is a variety of quartz with microscopic crystals.
In addition to the occurrences in West Virginia, there are extensive beds of Lithostrotionella in the geological regions called the St. Louis Limestone area, which covers much of the Midwestern United States, and the Little Valley Limestone area in Virginia.
Although not a faceted gemstone, lithostrotionella is often cut and polished for beads, pendants, and ornamental objects.
Crystal Structure: Hexagonal
Hardness (Mohs): 4
Color: Multiple colors, commonly white, red and black
Refractive Index: 1.486-1.658