A superb 'dog-tooth spar' Straw Stalactite form, originating from Guangdong province, China. These stalactites grew in caves, given a stable temperature and moisture the action of water permeating through a sedimentary host rock effectivly dissolved grain by grain and transported and redeposited on the cave ceilings, walls and floors the saturated solution creating stalactite and stalagmites. This process took thousands of years in some cases even millions of years creating large features. In this region of China feature rock of the Cambrian and Jurassic period, the mountains being laid down roughly 500 to 200 million years ago. Caves formed in the mountains and in the caves the stalactites formed. Precisely dating these features is difficult, if a cavern re-opened due to land movement the atmosphere changed and the minerals could slow or stop growing.
The process of growing a Straw Stalactite was that firstly the stalactite would form a smooth surface through deposition of the host rock sediments, later further crystallisation would take place and grow the dog-tooth crystals over the initially laid down surface. Crystal formations such as this need advantageous environments to grow, as mentioned above, once disturbed this changes the environment and the crystals alter or stop their growth cycle. Please read the accompanying document from Oxford University Museum of Natural History.