Tufa stone is a type of limestone that forms near bodies of water that contain a high concentration of dissolved minerals, particularly calcium carbonate. Tufa has a wide range of applications, from construction to art, and it’s fascinating to see in person. Tufa is not the same as tuff, a type of rock formed from volcanic ash, despite the fact that the two rocks have many similarities.
Mono Lake, a California lake known for its high concentration of dissolved minerals, contains some well-known examples of tufa. These minerals have precipitated out over time, forming distinctive tufa towers that tower over the lake. Tufa stone formations can also be found near springs, former waterways, and other lakes with a lot of dissolved minerals, and the shape of tufa stone formations is often quite fanciful, thanks to erosion and deposition processes.
Tufa formation can be influenced by a variety of factors. Minerals accumulate along a shoreline as a result of repeated wave depositions in many cases. Tufa stone can also form when extremely hot spring water enters a cooler body of water, causing the spring’s dissolved minerals to precipitate out, and tufa formations are common as bodies of water dry up, move, or recede.
This type of stone is usually soft and porous. Tufa’s porous nature makes it ideal for planters because it drains well rather than trapping water. Tufa can also be used as a sculpture medium, and it is also used as a casting medium by some jewelers. Jewelers and other metalworkers carve the desired shape into the rock, forming a two-piece mold, and then pour hot metal into the mold to cast with tufa stone. Tufa is soft, but it can withstand high temperatures, so it won’t crack or distort when used as a mold.
The stone has also been used as a building material in areas with large natural deposits of tufa. Some tufa stone structures are quite old, especially in desert areas where the arid conditions have prevented the tufa and the mortar used to cement it together from eroding. Tufa structures are occasionally embellished with intricate carvings and inlays, some of which have survived the test of time.
Tufa stone is available in a variety of sizes from rock shops and some art supply stores, as well as from construction companies on occasion.