Prepared under the auspices of the U.S. Department of State

Summary of the Reconnaissance Investigation of the 

Diamond Resource Potential and Production Capacity 

of Côte d’Ivoire

Introduction

This study presents the results of a multiyear effort to 

monitor the diamond mining activities of Côte d’Ivoire’s two 

main diamond regions, Séguéla and Tortiya. The innovative 

approach developed for this study integrates archival reports 

and maps, high-resolution satellite imagery, and terrain modeling to assess the diamond resource potential and production 

capacity of the Séguéla and Tortiya deposits.

Estimating Diamond Resource Reserves

A geologic resource assessment was conducted to calculate 

the remaining diamond reserves for Séguéla and Tortiya using 

archival geologic data, including gravel grade and thickness 

recorded by the Ivorian mining company Société pour le 

Développement Minier (SODEMI). These data were combined 

with terrain analysis and geomorphological maps in a geological 

process-driven model. After accounting for previous production, 

a total of 10,100,000 carats are estimated to be remaining in 

Séguéla and a total of 1,100,000 carats are estimated to be 

remaining in Tortiya, based on currently known deposits.

Production Capacity Assessment

Annual alluvial and primary diamond production was 

calculated for Séguéla and Tortiya for the years 2006 through 

2010 and 2012. Alluvial production in Séguéla was determined 

through the analysis of high-resolution satellite imagery to 

catalog the location and size of all active diamond mining 

pits (fig. 1). Annual production is calculated by multiplying 

the number of pits per year with grade and gravel thickness 

data. Primary production from Séguéla’s two actively mined 

kimberlite dikes, Bobi and Diarabana, was determined using 

high-resolution satellite imagery and digital elevation models 

to calculate the volume of excavated material. The volume 

was then multiplied by the grade of the deposits to arrive at the 

number of carats produced for the years 2006–2012. 

Bobi

Doualla

Diarabana

Area of 

detail

in B

A, Active mine sites interpreted from satellite imagery and 

represented by diameter. B, Area of detail showing active 

mine sites (circled areas) and currently inactive, previously 

mined pits (areas of dark reflectance).

Legbo R

Kodiouni R

EXPLANATION

Active pit—

 Diameter,

 in meters

4 to 5

5 to 10

10 to 15

15 to 20

20 to 25

>25

Kimberlite dike

A B

Background images from GeoEye 

IKONOS-2, March 6, 2006

Bobi Dike

Diarabana Dike 

0 1

0 0.5 1 MILE

2 3 KILOMETERS

0 100 200 METERS

0 250 500 FEET

N

Figure 1. Example of the use of satellite imagery to locate active pits in Côte d’Ivoire.

U.S. Department of the Interior

U.S. Geological Survey Printed on recycled paper

Fact Sheet 2012–3130

November 2012
A modified approach was implemented for the Tortiya 

study area. Data on the number of diggers, the number of days 

diggers work per year, the volume of material worked per 

digger per day, and gravel grade were combined to calculate 

production capacity. The results of the production capacity 

analysis for Séguéla and Tortiya are presented in table 1. 

Figure 2 displays alluvial, primary, and total production values 

for Séguéla from 2006 to 2012. Analysis was not completed, 

however, for 2011 due to a lack of available imagery. Figure 3 

displays the relation between alluvial and primary production in 

Séguéla and alluvial production in Tortiya.

The detailed analysis of production in Séguéla resulted in 

the identification of several notable trends. Total production in 

Séguéla increased by 75 percent from 2006 to 2009, dropped by 

10 percent from 2009 to 2010, then dropped by 40 percent after 

2010, returning to 2007 production levels. The discovery of the 

Diarabana Dike in 2009 is one influential factor leading to the 

peak in total production for that year. Following the discovery 

of the dike, alluvial production decreased, as more miners chose 

to exploit the richer primary deposits.

Figure 2.

0

50,000

100,000

150,000

200,000

250,000

300,000

Alluvial

Primary

Total

Analysis not complete for 2011 due to a lack of available imagery

 Production, in carats

Year

2006 2007 2008 2009 2010 2012

Table 1. Results of the production capacity analysis for Séguéla and Tortiya.

Year

Séguéla production 

(carats)

Tortiya 

production 

(carats)*

Séguéla and Tortiya 

production 

(carats)

Alluvial Primary Alluvial Alluvial and Primary

2006 61,704.75 9,656.00 19,687.50 91,048.25

2007 55,572.77 97,752.00 19,687.50 173,012.27

2008 25,957.70 166,604.00 19,687.50 212,249.20

2009 47,514.16 220,937.00 19,687.50 288,138.66

2010 23,925.23 220,937.00 19,687.50 264,549.73

2012 19,100.47 134,601.00 19,687.50 173,388.97

*Due to constraints on the availability of data, a range of production was calculated for 

Tortiya. The annual average of this range is presented in this table.

Figure 2. Alluvial production, primary production, and total 

production for Séguéla from 2006 to 2012.

2006 2007 2008 2009 2010 2012

Year

Tortiya

Séguéla (Primary)

Séguéla (Alluvial)

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Figure 3.

 Production, in carats

EXPLANATION

Figure 3. The relation between Séguéla alluvial production, 

Séguéla primary production, and Tortiya production.

Conclusion

This study presents a methodology for calculating the 

resource reserves and production capacity of Séguéla and 

Tortiya. While this analysis incorporates the best available 

data, significant data gaps remain. The acquisition of additional 

geologic and geomorphic data would improve the results of the 

study, which will be updated should such data become available.

Peter G. Chirico

12201 Sunrise Valley Drive

National Center, MS 926A

Reston, VA 20192

pchirico@usgs.gov

Additional Information

Katherine C. Malpeli

12201 Sunrise Valley Drive

National Center, MS 926A

Reston, VA 20192

kmalpeli@usgs.gov