Stalactites (Figure 2.54), also known as stalactites and travertine, refer to different forms of calcium carbonate deposits such as stalactites, stalagmites and stone pillars formed in caves in carbonate rock areas under long geological history and specific geological conditions. Putting stalactites on the desk as ornamental stones was first seen in Song Dynasty. Du Wan's "Yunlin Stone Spectrum": "Its quality is quite sharp, or there are three sides on the side of the plaque, and the texture is like brushing silk, hiding the stone surface, or rinsing the road, buckling it or making a sound, the stone color is uncertain, and there are four sides occasionally." In the Qing Dynasty, Chen Ju wrote in the Records of the Heavenly Stones: "In the cave of the stone dragon, it is as sharp as a bamboo shoot, several inches long, and there are also more than feet, and there are many fine holes around it." Stalactites that cannot be moved in caves should strictly belong to the category of landscape stones, not ornamental stones. The underground karst terrain in Guangxi, Yunnan and other provinces produces abundant stalactites. Underground karst is karst cave, which is a cave formed by long-term dissolution and erosion of groundwater along limestone layers or cracks. The main component of limestone is calcium carbonate. When it meets water with dissolved carbon dioxide, it will react to generate soluble calcium bicarbonate, and the chemical formula is CaCo3+CO2+H2O = Ca (HCO3) 2. When the water dissolved with calcium bicarbonate is heated or the pressure suddenly decreases, the calcium bicarbonate dissolved in the water will decompose, release carbon dioxide, and regenerate calcium carbonate to precipitate. The water at the top of the cave slowly seeps under the action of gravity, and with the evaporation of water, the dissolved calcium in the supersaturated solution becomes solid again (that is, solidified). Under the premise of suitable growth environment, stalactites and stalagmites can only grow less than 1mm every year, so it takes at least tens of thousands of years or even longer to form them. With the passage of time, these sediments will form a variety of spectacular stalactite oceans. Some are deposited at the top of the cave and grow from top to bottom, which is called stalactite; Some are deposited at the bottom of the cave and grow in a bamboo shoot shape from bottom to top, which is called stalagmite; If the corresponding stalactites are connected with stalagmites, a stone pillar is formed, also known as Ganoderma lucidum pillar. If groundwater slowly flows down or seeps out of the cave, it will form a curtain-like calcium carbonate deposit on the cave wall-stone curtain (also known as stone curtain). Some stone curtains are like solidified waterfalls, so they are also called "stone waterfalls". Some caves often have springs at the bottom, and calcium carbonate dissolved in the spring will form "stone flowers" around the spring eye.
Stalactites often have different colors due to different mineral components, such as milky white, light red, light yellow and reddish brown, and some colors are mixed, forming colorful patterns. Its shapes are various, such as bamboo shoots, columns, curtains, grapes, and others like all kinds of flowers, animals and people, which are clear and lifelike (Figure 2.55). It is hard and easy to smash, with a flat cross section, white to light grayish white and slightly light brown. It has a star-shaped light for light observation, and there are often round holes near the center. There are many light orange concentric rings around the round holes, and some can be seen with radial textures. It is better to be snow-white and crystal-clear, which is also called crystal stone by the people and has high ornamental value. Biye "Fuchun River"? "Curling" and "Shuanglong" contain "stalactites everywhere in the cave, which are moist and fresh. Some of them are like jade pillars hanging vertically from the top to the ground, some are like rain clouds hanging upside down in the air, and some are like white waves surging and surging into the sky. It is really colorful and spectacular."
stalactites were regarded as medicinal stones by the ancients, and there are many medical records from Shennong Materia Medica to Compendium of Materia Medica. Liu Zongyuan's book on stalactites with Cui Raozhou in the Tang Dynasty wrote that a small amount of it can "make people glorious and gentle, make their qi flow freely, stimulate their stomachs and intestines, live a good life and be healthy, feel at ease and enjoy themselves". Stalactite is one of the main components of "Five Stone Powder" smoked by celebrities in Wei and Jin Dynasties. "Bielu" holds that the efficacy of stalactites is: "Yiqi, tonify deficiency, treat foot weakness, pain and cold, burn down, and strengthen yin. Confucius' evil deeds, male vulvar sores, female vulvar erosion, and bulimia often want to sleep. Yin, the main foot is cold and weak. " There is also a record about the efficacy of stalactites in "Seeking the Origin of Materia Medica": "Warming the lungs to absorb qi, treating lung cold, relieving cough and clearing phlegm."
The formation of stalactites is extremely difficult. Protecting it is equivalent to protecting a precious gift given by nature. In 22, the Standing Committee of the People's Congress of Guangxi Zhuang Autonomous Region passed the Regulations on the Protection of Stalactite Resources in Guangxi Zhuang Autonomous Region, which came into effect that year, stipulating: "Stalactite resources belong to the state, and it is forbidden for any organization or individual to occupy, destroy or exploit them without authorization; The survey and design of major projects such as railways, highways, bridges and airports should avoid the stalactite caves that have been discovered. "
Interesting story of the stone: There are many cracks on the top of the stalactite-meeting cave, and water drops are constantly oozing out from each crack. Whenever the water evaporates, some calcium carbonate precipitates are left there. One drop, two drops, three drops ... The water keeps appearing and volatilizing, and the calcium carbonate on the ceiling of the cave accumulates more and more, finally forming a nipple-the stalactite of childhood. Then, the nipple is covered with layers of calcium carbonate, which makes it hang longer and longer, even reaching several meters.
stalactites can be divided into "living" and "dead". The "living" stalactites can still seep under water and can "grow", while the "dead" stalactites can't "grow" without dripping under water. Stalagmites are close partners of stalactites. When the water drops on the roof of the cave fall, the residual calcium carbonate begins to deposit on the ground. Stalagmite grows upward against stalactites at the position where water drops. Because of its large chassis, stability and not easy to break, its growth rate is often faster than stalactites. The maximum height of stalagmites can reach 3m, like a stone pagoda growing out of the ground.
Stalactites that grow downward sometimes connect with stalagmites that grow upward to form a stone pillar, which is thick at both ends and thin in the middle. People have given it a nice name "Happy Meeting". Sometimes, although they grow opposite to each other, because the ceiling of the cave is no longer dripping, they can't grow, and they can't be connected. People call stalactites "tears have dried up" and stalagmites "eager to wear". Because stalactites grow very slowly, only 1 cm long in hundreds of years, it is really necessary to look through the autumn water to connect them.
In many limestone caves, stalactites are broken or too much calcium carbonate blocks the path of water droplets, which can also cause stalactites and stalagmites not to be connected together. Because the water drop was forced to change its path and move elsewhere, a new stalactite grew. In this way, stalactites and stalagmites will never "meet".