Grain composition and surface characteristics of musical sand

Abstract

A judicious choice of factors considered essential for producing musical sounds has led to an experimental procedure which creates musical sands from previously silent ones. An analysis of this procedure provides evidence that the composition of the sand grains aid the condition of the grain surfaces play a delicate role. X-ray fluorescence tests have revealed that the best musical sands are primarily quartzitic. Repeated wetting and drying action allows silica to abrade softer feldspars and this forms fine dust which is removed by milling and by renewing the water. It also appears that, as water dries on the grains of sand, the surfaces are coated with an extremely thin film of salts and water in an amorphous silica layer. Preliminary infrared spectroscopic studies of the surface of different types of booming and singing sands are reported. These results lead to the conclusion that the music is generated by the rubbing together of the surfaces of millions of grains of quartz with particular composition and surface characteristics. Knowledge of the musical sand phenomenon may be useful in understanding the mechanics of many other granular system and numerous other processes in geology and technology.