Rock varnish on architectural stone: microscopy and analysis of nanoscale manganese oxide deposits on the Smithsonian Castle, Washington, DC

Heritage Science

Table 1 INAA bulk chemistry for architectural Seneca sandstone used for two Washington, DC structures expressed as weight per cent

Oxide/El	Castle₁	Castle₂	Castle_avg	DC jail₁	DC jail₂	DC jail_avg	Overall_avg
SiO ^a₂	56.26	53.36	54.81	57.76	57.40	57.58	56.20
Al₂O₃	22.94	25.05	24.00	23.21	23.26	23.24	23.62
CaO	0.58	0.64	0.61	0.33	0.23	0.28	0.45
MgO	0.16	0.20	0.18	0.00	0.00	0.00	0.09
Fe₂O ^b₃	6.15	6.53	6.34	4.57	4.61	4.59	5.47
K₂O	2.83	2.91	2.87	3.26	3.84	3.55	3.21
Na₂O	10.22	10.41	10.32	10.12	9.92	10.02	10.17
TiO	0.75	0.78	0.77	0.62	0.62	0.62	0.69
MnO^c	0.04	0.04	0.04	0.06	0.05	0.06	0.05
Fe	4.30	4.57	4.43	3.20	3.22	3.21	3.83
Mn	0.03	0.03	0.03	0.05	0.04	0.05	0.04
Fe/Mn	138.76	147.43	143.14	68.79	83.27	69.09	98.80