Identification of artificial orpiment in the interior decorations of the Japanese tower in Laeken, Brussels, Belgium

Heritage Science

Table 1 Recapitulative table for the two reference materials and the 3 representative types of arsenic sulfide/techniques found in the decorative panels of the Japanese tower in Laeken, Belgium

	Natural orpiment Kremer	g-As _x S _x laboratory-made	C90.058/P210.011	C90.101/P209.073
Particle shape	- Thin and elongated forms	Various shapes from spherical to sharp-edged	- Round to elliptical-shaped particles
	- Laminated masses or granular and powdery with a fibrous structure (Figure 4a)	Various shapes from spherical to sharp-edged	- Spherule can be smooth and round
		(Figure 4c)	- Spherule can be smooth and round
			- Both round and sharp edges
			- Irregular sizes
	- No smooth and round structures		- Figure 3
Raman wavenumbers	136, 154, 179, 202, 293, 311, 354, 367 (sh), 383 cm⁻¹	220, 235, 339, 367 (sh), 473 cm⁻¹	234, 337, 362 (sh), 471 cm⁻¹	218, 234, 337, 362 (sh), 471 cm⁻¹
Raman wavenumbers	(Figure 6a)	(Figure 6b)	(Figure 5a, b)	(Figure 5c)
PLM characteristics	- Birefringent	- Strong refraction	- Isotropic and amorphous
	- Anisotropic	- Isotropic and amorphous	- No interference colors
	- Bright pink and green to blue interference colors	- No interference colors	- Full extinction
		- No interference colors	- Compressed corners and edges resulting from crushing spherical particles
		- Roundish morphology
	- Foliated, micaceous structure	- Roundish morphology
	- Foliated, micaceous structure	- Brittle, jagged fracture behavior	- Figure 8
	- Ductile when exposed to mechanical strain	- Brittle, jagged fracture behavior
	- Ductile when exposed to mechanical strain	- Figure 7b
	- Figure 7a	- Figure 7b