Magical/ritual lore: Stalactites, (which hangs from cave roofs) and stalagmites (which project up from the floors of caverns) are produced by lime-rich water dripping into caves from above. Over eons, the produced masses of calcite familiar to anyone who has entered such a cave. Sometimes they meet and form columns of stone.
In the past they were thought to be petrified earth. One hundred years ago it was an common practice for cave visitors to break them off as souvenirs. Such needless, senseless destruction has, hopefully, ended.
Historically, small stalagmites and stalactites were carried, often in small bags, as amulets against negativity and “evil”. Their phallic shape probably contributed to their protective properties in the popular mind. This is ancient magic and is included (…) because of it’s historical interest. There’s no reason to destroy the beauty of caves for magical purposes. Substitute any other protective stone.
(Source: Cunningham’s Encyclopedia of Crystal, Gem, and Metal Magic)