OBSIDIAN BUTTE

IMPERIAL COUNTY,

SOUTHEASTERN CALIFORNIA

This prehistorically popular, somewhat vitrophyric obsidian source has been covered in fine detail by Richard Hughes. I refer you to his paper. We have a good source standard data library for this source at Berkeley, and routinely analyze archaeological collections from San Diego, Imperial, and Riverside Counties:

Hughes, Richard E. (1986). Trace element composition of Obsidian Butte, Imperial County, California. Southern California Academy of Science Bulletin 85:35-45.

In December 2009 the samples originally collected in the 1980s were re-analyzed on the ThermoScientific Quant'X for both oxides and trace elements as seen below.  This mildly peralkaline obsidian exhibits a unique elemental composition in the region.

Raw elemental concentrations for Obsidian Butte source standards, and RGM-1 USGS obsidian standard. All measurements in parts per million (ppm). 

Sample

Ti

Mn

Fe

Zn

Rb

Sr

Y

Zr

Nb

Ba

Pb

Th

OB-1

1183

403

17247

78

134

26

116

331

31

641

18

23

OB-2

1664

438

21732

76

125

53

98

422

30

727

24

18

OB-3

1640

449

21495

76

132

52

100

435

27

767

19

18

OB-4

1435

410

19807

78

137

28

125

369

35

594

19

20

OB-5

1366

406

18883

73

126

45

105

377

26

702

20

17

OB-6

964

365

14559

72

131

20

119

303

33

552

20

26

OB-7

1464

424

19694

71

122

46

94

419

22

730

18

20

OB-8

969

381

16358

80

148

20

133

313

35

625

21

20

OB-9

1598

422

19922

75

121

47

98

415

24

684

19

15

OB-10

1467

401

19067

68

121

48

94

405

21

701

19

23

OB-11

1358

387

17890

75

133

41

113

355

29

685

19

24

OB-12

1758

462

22674

81

129

51

100

437

27

804

17

24

RGM1-S4

1482

290

12850

39

151

107

21

223

12

893

27

19

 Mean and central tendency for the Obsidian Butte data shown in the table above.

 Selected major oxides for sample Obsidian Butte-9 (OB-9)

Sample

SiO2

Al2O3

CaO

Fe2O3

K2O

MgO

MnO

Na2O

TiO2

Obsidian Butte, CA

 

 

 

 

 

 

 

 

 

OB-9

73.846

12.485

1.163

2.951

4.358

<.001

0.067

4.402

0.239

RGM1-S4

75.680

12.477

1.3024

1.806

4.550

<.001

0.0379

3.77

0.196

  

This page maintained by Steve Shackley (shackley@berkeley.edu).
Copyright 2009 M. Steven Shackley. All rights reserved.
Revised: 18 December 2009

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