i‘ve seen it before but cant remember what its called
check where the bike came from DUH!!!
Do a web search (company name) tire company.
My guess is that it was made in China. It's a wild guess because too much stuff comes in from foreign imports, hence a massive defficit.
4 types may be what you are looking for, coquina, pisolitic limestone, oolite, or fossiliferous limestone. Coquina is mainly composed of mineral calcite, often including some phosphate, in the form of seashells or coral. Oolite (egg stone) is a sedimentary rock formed from ooids, spherical grains composed of concentric layers.Ooids are most commonly composed of calcium carbonate (calcite or aragonite), but can be composed of phosphate, chert, dolomite or iron minerals, including hematite. Dolomitic and chert ooids are most likely the result of the replacement of the original texture in limestone. Pisolitic Limestone Pisolitic limestone is white or yellowish brown. Its texture is made interesting by pisolites, spherical bodies over 2 mm in diameter made out of calcium carbonate. Pisolitic limestone comes from the precipitation of calcite and other minerals from warm, turbulent water. It's found in the Bahamas, the Great Barrier Reef of Australia and in some European hot springs. Pisolitic limestone is only of interest to collectors, because it has no industrial value. Fossiliferous and Compact Limestone Fossiliferous limestone can come in many colors ranging from white to black, depending on the minerals contained in it. The rock often has cavities because the fossils in it have dissolved. In many specimens the fossils can be clearly seen as shells or skeletons or imprints. Fossilized limestone found in the Nile Valley was used to build the pyramids, and this sort of limestone in general is very good for construction work. When crushed, it's good for ballast for roads and railroads. Compact limestone is hard, comes in many colors and has a very fine grain. It is often cut into slabs, polished and used like marble
