Table 1

The major elements of volcanic ashes and control minerals (as % oxide by weight) as determined by XRF

Element	Cris/obs	Anorthite	Labradorite	Montserrat 1	Montserrat 2	Antigua
*Cristobalite/obsidian.
SiO₂	75.69	57.48	54.82	64.83	60.60	58.46
Al₂O₃	12.94	25.69	27.64	15.96	18.51	18.70
Fe₂O₃	0.94	0.39	0.41	6.00	6.65	7.34
MnO	0.06	0.01	0.01	0.15	0.16	0.16
MgO	0.03	0.07	0.12	2.30	2.62	2.78
CaO	0.73	7.99	10.23	5.50	7.33	8.51
Na₂O	3.06	5.19	4.17	2.50	2.65	2.39
K₂O	4.45	0.56	0.51	1.04	0.82	0.71
TiO₂	0.06	0.10	0.12	0.51	0.56	0.66
P₂O₅	0	0.01	0.02	0.14	0.13	0.12