Dave Bunnell has an awesome site dedicated to caves and lava - this one above is a picture of tubular lava helictites:
Helictites are an eccentric or "vermiform" form of stalactite that twists and turns rather than growing straight up and down. They typically begin as tubular lava stalactites, but crystallization of the emerging lava as it cools pushes the lava in different directions. Often groups of these helictites will bend in the same direction down the passage, suggesting an influence of wind moving through the tube.
The Black Chasm cave in California is loaded with Helictites. Here's a few pics: http://www.ruama.com/gallery/610668/2/25818160 http://www.ruama.com/gallery/610668/1/25818136 http://www.ruama.com/gallery/610668/2/25818139 http://www.ruama.com/gallery/610668/2/25818150 http://www.ruama.com/gallery/610668/2/25818157
http://www.ruama.com/gallery/610668/2/25818160
http://www.ruama.com/gallery/610668/1/25818136
http://www.ruama.com/gallery/610668/2/25818139
http://www.ruama.com/gallery/610668/2/25818150
http://www.ruama.com/gallery/610668/2/25818157