Kalktuff (Calcareous Tufa)
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Mineral NameKalktuff (Calcareous Tufa)
Chemical FormulaCaCO3
Mohs Hardness3
Streak Colorwhite
Cleavageperfect rhombohedral (for constituent calcite)
Fractureuneven, earthy, porous
Specific Gravity2
Colorsbrown, tan, grayish-white, green (due to moss)
Transparencyopaque
Type LocalityWorldwide, wherever calcium-rich freshwaters occur
Mineral GroupCarbonate rock
Usesbuilding material, decorative stone, soil amendment
Associated Mineralscalcite, aragonite, organic matter (plant remains)
Raritycommon
Description
A light-colored, highly porous sedimentary rock, exhibiting a rough, earthy fracture surface with shades of brown and tan, and a grayish-white exterior often covered in moss.
Geological Context
Forms in freshwater environments, such as springs, rivers, and lakes, through the rapid precipitation of calcium carbonate, often facilitated by biological activity like algae and mosses.
