Slide 1: Application of the microdiamond technique in assisting diamond mining juniors
Application of the microdiamond technique in assisting diamond mining juniors to make rapid technical and economic decisions H. Cronwright and J.A.H. Campbell Hilde Cronwright presenting to SAIMM “Diamonds: Source to Use” 13 June 2018 Copyright © The MSA Group No part of this publication may be repr
Slide 2: Introduction
INTRODUCTION • Frischgewaagt kimberlite dyke in Limpopo, RSA – Explored by Vutomi Mining (Pty) Ltd & Botswana Diamonds plc • Microdiamond analysis (MiDA) technique, • Combined with – macrodiamond results from two surface sampling programmes (SSP’s) – geological information (petrography) – size-frequ
Slide 3: Frischgewaagt Kimberlite
FRISCHGEWAAGT KIMBERLITE Thorny River Frischgewaagt Marsfontein Klipspringer Mine Hilde Cronwright – SAIMM Diamonds Source to Use June 2018
Slide 4: Thorny River Project Location
THORNY RIVER PROJECT LOCATION Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 5: Frischgewaagt Kimberlite Dyke
FRISCHGEWAAGT KIMBERLITE DYKE Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 6: Historical Work Done
HISTORICAL WORK DONE • Previous Work Done by Vutomi – Several phases of drilling – Heavy Mineral Analysis by MSA – Kimberlite Indicator Mineral (KIM) Chemistry Analysis by UJ Evaluation of Kimberlite Discoveries • Indicator mineral Chemistry / Diamond Potential Walk away • Prioritise kimberlites for
Slide 7: The MSA Group – Diamond Exploration Lab
THE MSA GROUP – Diamond Exploration Lab The MSA Group Diamond Analytical Services ISO17025 Accredited since May 2012 Accreditation No. T0544 Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 8: Sampling Results – MinChem (1)
SAMPLING RESULTS – MINCHEM (1) • KIM Chemistry: 209 PERIDOTITIC GARNETS 8% 18% A-C From Westerlund (2000) Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 9: Sampling Results – MinChem (2)
SAMPLING RESULTS – MINCHEM (2) • KIM Chemistry: 42 ECLOGITIC GARNETS 42% A-C From Westerlund (2000) Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 10: Sampling Results – 2015 SSP
SAMPLING RESULTS – 2015 SSP • 2015 Vutomi Surface Sampling Programme • 3,647 t material processed • 466 macrodiamonds recovered from surface sampling, • 236 carats • 6.5 cpht for the dyke sampled • Valued at $180/ct Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 11: Sampling Results – 2015 SSP
SAMPLING RESULTS – 2015 SSP • 2015 Vutomi Surface Sampling Programme • In-situ grade estimation required several supporting estimates – Mass of material sampled – Visual estimation of contamination & dilution – Compensating for scrubber oversize & processing losses • Actual mass kimberlite processed
Slide 12: Sampling Results - BOD
SAMPLING RESULTS - BOD • 2017 Sampling carried out by Botswana Diamonds PLC (BOD) – Ground Geophysics – Percussion and core drilling – Petrographic analysis • Group 2, coherent hypabyssal (magmatic) kimberlite (Robey, 2017). • Compared with historical data from Marsfontein and Klipspringer ➢ indicat
Slide 13: Sampling Results - BOD
SAMPLING RESULTS - BOD • 2017 Sampling carried out by Botswana Diamonds PLC (BOD) – Microdiamond analysis Evaluation of Kimberlite Discoveries • Indicator mineral Chemistry / Diamond Potential Walk away • Prioritise kimberlites for evaluation Walk away • Microdiamond Analysis (MiDA) Walk away • Surf
Slide 14: Microdiamond Analysis
MICRODIAMOND ANALYSIS • MSA established first MiDA lab in 2006 (SGS South Africa) • Since 2016 custom-built facility operated by Min-Met Equipment (Pty) Ltd • The only Caustic Fusion and MiDA lab in Africa Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 15: Microdiamond Analysis (continued)
MICRODIAMOND ANALYSIS (continued) • Synthetic diamond QC Spikes • All stones screened, measured (X,Y,Z) described and weighed • Diamonds stored on mineral cards and data captured Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 16: Microdiamond Results
MICRODIAMOND RESULTS • Microdiamond analysis • 160kg core • From ’Dyke Proper’, ’Central Blow’ and ’Second Blow’ • 223 microdiamonds recovered • 98% QC spikes recovered • Screened (Taylor sieves) Sample Sample Weight Total # Diamond Size Fractions (mm) location ID (kg) diamonds 1.18 0.85 0.6 0.425 0
Slide 17: Preliminary Grade Estimation (1)
PRELIMINARY GRADE ESTIMATION (1) • Preliminary Grade Estimation by Ferreira – Mida results together with macrodiamonds from 2015 SSP – Preliminary grade estimation – Early stage exploration evaluation to determine if further work is warranted – Modelling done with various methods • Using avg stone d
Slide 18: Total Diamond Content Model
TOTAL DIAMOND CONTENT MODEL Range: 20 – 270 cpht Uncertainty in grade due to Microdiamond data points • Small sample size • Low stone counts Maximum MiDA Model • Nature of distribution of (individual MiDA points) stones in size classes Macrodiamond data points from 2015 SSP Note: The upper end of th
Slide 19: Refinement of Grade Estimation (2)
REFINEMENT OF GRADE ESTIMATION (2) • Refinement of Preliminary Grade Estimation by Petersen – Modelling repeated using empirical data – Insufficient +1-3mm stones from 2015 SSP to anchor model – historic total content data used as proxy to bridge micro- and macrodiamond datasets – Grade refined to 7
Slide 20: BOD 2017 Surface Sampling
BOD 2017 SURFACE SAMPLING • Surface Sampling Programme by BOD in November 2017 • 42 m trench along strike of Frischgewaagt dyke • 305 dry tons of kimberlite and host rock Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 21: BOD 2017 Surface Sampling
BOD 2017 SURFACE SAMPLING – Aim to provide additional confidence to 2015 macrodiamond results • processing accurately known quantity kimberlite • recover stones 1-3mm size fraction (link up the MiDA – macro models) • refine the grade estimate • estimate the true total diamond content (TTC) • recover
Slide 22: BOD 2017 Surface Sampling
BOD 2017 SURFACE SAMPLING • Surface Sampling Programme Macrodiamonds • 512 macrodiamonds recovered • 62 carats • Recovered diluted grade of 20.7 cpht • +11 Diamond Sieve +9 Diamond Sieve Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 23: Grade Estimation (3)
GRADE ESTIMATION (3) • Grade estimation using 2017 SSP data (Peterson, 2017) • Biggest uncertainty in calculating in-situ kimberlite grade is dilution of kimberlite sample. • uncertainty in contact between weathered kimberlite dyke and host rock – gradational boundary of kimberlite, – parallel fault
Slide 24: Grade Estimation (3 continued)
GRADE ESTIMATION (3 continued) – External dilution calculated: planned vs actual size sample – Proportion of kimberlite: estimated volume of kimberlite volume of excavation From Petersen (2017) Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 25: Grade Estimation (4 continued)
GRADE ESTIMATION (4 continued) • Determine actual quantity of kimberlite mined (Coward) • Combine undiluted grade with – Metallurgical process efficiencies – modelled SFD ➢ Undiluted in-situ Total Content grade range of 46-74 cpht (at BCOS of +1 mm) (Coward, 2018) • Published resource grade of nearb
Slide 26: Macrodiamonds vs Microdiamonds
MACRODIAMONDS vs MICRODIAMONDS • Valuation of 83 diamonds (54.32 ct) by QTS Kristal Dinamika (Ferraris & Bouquet, 2017) • Crystal shapes compare well with microdiamonds Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 27: FTIR of Microdiamonds
FTIR of MICRODIAMONDS • Fourier transform infrared spectroscopy (FTIR analysis) • Type II microdiamonds present • Type 0.150mm microdiamonds Type I Type II Hilde Cronwright – SAIMM Diamonds Source to Use_June 2018
Slide 28: Summary
SUMMARY 2017 In-situ grade Geophysics (estim) 62 cpht Core Drilling Petrography 2014 HMA & 2015 SSP (Vutomi) 2017 CF & MiDA MinChem 3647 t 160 kg 209 Gar 466 macros / 236 ct 223 MiDA’s 18% G10D 6.5 cpht In-situ Grade Initial Grade 46 - 74 cpht Estim (Ferreira) Adjust for dilution, (at BCOS +1mm) 20
Slide 29: Conclusion
CONCLUSION • MiDA is highly recommended by MSA for first stage cost effective evaluation of kimberlites – Establish whether newly discovered kimberlite body (dyke or pipe) is barren or diamondiferous – helps prioritise targets for bulk sampling or “walk away” decision – diamond content estimation of
Slide 30: Conclusion (continued)
CONCLUSION (continued) • Early project evaluation using MiDA combined with – Geological information (spatial distribution, petrography, mineralogy) – Historical diamond size frequency distributions (e.g. Klipspringer) – Early stage diamond population characterization • Provide a better understanding
Slide 31: Conclusion (continued)
CONCLUSION (continued) • BOD 2017 SSP yielded insufficient macrodiamonds for valuation and resource estimation (62.88 ct) BUT • Combined with MiDA data the total carat content (TCC) range could be calculated (46-74 cpht) • This project illustrates how microdiamond analysis was crucial for a prelimin
Slide 32: Questions
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