The composition and texture of tube-like structures found in chemical gardens has been uncovered. 

So-called silica gardens are demonstration experiments familiar to many. The life-like appearance of the tubular structures - which are formed by precipitation when salt crystals are added to a silicate solution - has interested scientists for centuries, but little is known about their chemical composition according to Oliver Steinbock and colleagues at Florida State University, Talahassee, US. 

By using a seed solution instead of a seed crystal, the researchers grew tubular crystal formations in a reproducible way, and studied their composition by electron microscopy and Raman spectroscopy.

The scientists found that their tube walls consist of copper hydroxide, which is stabilized by a thin exterior silica layer. They also found intricate nanorod structures and discovered that the outside surface of the walls has a striped texture, the origin of which is still unknown. 

Steinbock says that understanding how these chemical gardens grow and what they are made of is of fundamental interest, and might be valuable for technical applications. 'Being able to create such structures on a micrometre-scale could open up many promising research directions,' he said. 

Steinbock is also interested in how these chemical gardens relate to other precipitation processes that occur in nature. 'We are curious about similarities of our experiments and tubular structures in geochemical and biological systems such as black smokers at hydrothermal vents and marine algae,' he added. 

Caroline Moore