Table 3.4.

Composition of a volcanic ash sample collected during the eruption of Mt. St. Helens (Washington, USA) on 19 May 1980.

Constituent	Particulate sample	Average ash
Major elements (%)
SiO2	≡ 65.0	65.0
Fe2O3	6.7	4.81
CaO	3.0	4.94
K2O	2.0	1.47
TiO2	0.42	0.69
MnO	0.054	0.077
P2O5	–	0.17
Trace elements (ppm)
S	3220	940
CI	1190	660
Cu	61	36
Zn	34	53
Br	< 8	~ 1
Rb	< 17	32
Sr	285	460
Zr	142	170
Pb	36	8.7

Source: From Fruchter et al. (1980) and Hooper et al. (1980).