向光性钟乳石常见于有明暗光线区别的洞口位置，因藻类等低等向光性生物附着生长，由植物光合作用吸取洞顶滴水中的CO2，引起滴水过饱和而沉积的钟乳石，向下生长时斜向洞外，属生物岩溶形态。黑岩穿洞出口处可见悬挂钟乳石，具有明显的向光性。 The heliotropic stalactites are often found at the entrance of the cave with the difference of light and dark light. Due to the attached growth of lower heliotropic organism such as algae, the photosynthesis of the plants absorbs the CO2 in the water drops of the cave top, then stalactites are formed resulted from supersaturated water drops, and grow downward and oblique to the outside of the cave. The stalactite belongs to biological karst form. The stalactites were hung at the exit of the Heiyan light-through cavity and have obvious phototropism.