Stalagmite

Stalagmites are typically composed of calcium carbonate, but may consist of lava, mud, peat, pitch, sand, sinter, and amberat (crystallized urine of pack rats).

Oils and dirt (mud, clay) from human contact can also stain the formation and change its color permanently.

Their mineralogical composition, close to that of siliceous minerals commonly found in basalt (for example, obsidian), the main constituent of volcanic glass, is different.

However the difference from calcareous stalagmites is that the transport of siliceous material occurs in the molten state and not dissolved in aqueous solution; CO2 degassing does not play any significant role.

The generic term "lavacicle" has been applied to lava stalactites and stalagmites indiscriminately, and evolved from the word "icicle".

Ice stalagmites are more common than their stalactite counterparts because warmer air rises to the ceilings of caves and may raise temperatures to above freezing.

[13] Secondary deposits, which create stalagmites, stalactites, flowstone etc., outside the natural cave environment, are referred to as "calthemites".

[9] The largest known stalagmite in the world exceeds 70 metres (230 ft) in height and is in Sơn Đoòng Cave, Vietnam.