What is a stalactite in geology ?

Stalactite : definition

This term refers to aggregates of minerals arranged in columns, cones or elongated cylinders. Calcite and aragonite stalactites are found in caves where they can measure several tens of meters. When the concretion forms from the ceiling it is called a stalactite while when it forms from the ground it is called a stalagmite. Their internal texture is variable : radiated, concentric, grainy, sometimes monocrystalline, etc... Many mineral species can produce stalactites such as rhodochrosite, malachite, chalcedony, goethite, etc...
Malachite stalactites from Katanga, Congo
Chalcedony stalactite from Nasik, Maharashtra, India
Monocrystalline calcite stalactite from Cadacu, Gard, France