OBSIDIAN 55 
Table 4. Cluster statistics — mean values and standard deviations (in brackets). 
Cluster 1 = Great Barrier I 2 = Mayor I 
Major elements (wt. %) 
Si0, 1533. (02533) 73.89 (1.1916) 
TiO, 0.11 (0.0075) 0.22 (0.0110) 
Al,O3 12.69 (0.1245) 10.21 (0.4464) 
Fe,0,* 1.43 (0.0339) 5.03 (0.6351) 
MnO 0.03 (0.0041) 0.10 (0.0167) 
MgO 0.18 (0.0293) 0.10 (0.0251) 
CaO 0.71 (0.0366) 0.21 (0.0055) 
Na,O 3.89 (0.0758) 5.89 (0.1978) 
K,0 4.78 (0.0674) 4.38 (0.0594) 
P,0; 0.03 (0.0052) 0.02 (0.0045) 
Trace elements (ppm) 
Ba* 450.22 (43.7560) 296 122278) 
Rb 195.03 (1.1343) 133.94 (4.8433) 
Sr* 24.73 (4.2378) 0.42 (0.9391) 
Pb 24.18 (1.3674) 26.42 (0.6301) 
Th 20.78 (2.9376) 14.82 (1.7964) 
Zr 135.32 (3.5841) 1051.82 (75.5082) 
Y 35.55 (1.6059) 131.10 (9.4578) 
La 36.12 (2.2498) 91.60 (4.8420) 
v* 0.82 (1.2750) 0.18 (0.4025) 
Crt 2.18 (3.4249) 0.00 (0.0000) 
Ni* 2.32 (3.6750) 6.38 (3.7519) 
Cu* 8.97 (2.5367) 5.00 (4.7582) 
Zn 37.65 (1.1327) 231.92 (21.2649) 
* = may be invalid due to being bdl 
source. They cite the discovery of new obsidian sources as contributing to this change, 
with the additional factor, noted by Seelenfreund-Hirsh (1985), being restriction of 
access due to the increase of warfare and territoriality in later prehistory. 
Acknowledgements. | thank L. Furey and Dr N. Prickett for making the Westfield obsidian 
pieces available, and providing stimulating discussion relevant to obsidian sources. Prof. R. 
Green made obsidian from the collection of the Anthropology Department, Auckland 
Univeresity available to me, and critically read the draft of this paper. 
