Are there more than one kind of stalactites?

Answer 1

O)h yes. Sticking for the moment to the most common speleothems, those formed from calium carbonate in its crystalline variety, calcite:

They come in many shapes and sizes, as well as the typical icicle or carrot shape. The finest are delicate, hollow tubes of calcite perhaps just a few mm in diameter, called "straws" in Britain and "soda straws" in the USA. If the calcite solution trickles down an overhanging wall, it can form "curtains" (aka "draperies") from their general shape. These can be pure white or banded by minerals; and translucent to a strong light. Curtains sometimes develop curious little teeth-like projections along their edges. Oddest are "helictites", which as the "heli" part suggests, grow into strangely twisted forms, often horizontally, and no-one has really managed to explain how they develop since a theory that suits one group of helictites may not work for another!

A rarer form is the "anthodite", a mass of radiating crystals of Aragonite (another form of calcite). Spray can produce "botryoidal" formations, resembling miniature cauliflower heads.

I have seen one set of tiny but exquisite helictites, in a cave in marble in Norway, where stalactites are unusual. They were barely 20mm high, shaped rather like processional church crosses with a central stem and cross-arm. The head of the stem and the arm tips each bear a tiny little botryoid. I think I tried to photograph them but without success.

Gypsum (calcium sulphate) rock is soluble in water, and caves can form in it. The formations in such caves can be exquisitely beautiful crystal displays. Gypsum in its Selenite variety will also form very long needle-like crystals, sometimes found growing from clay containing the mineral. I think most of the speleothems in Lechaguilla Cave are of gypsum or other non-calcite minerals, thanks to that cave's development by highly acidic, mineral-rich hydrothermal water rather than the much more common rain-water.

A cave formed very unusually in rock salt has been discovered recently in Iran, and it is blessed with extremely beautiful salt-crystal formations.