Automated Mineralogy and Petrography

Bringing automated mineral liberation analysis to your SEM

SEM, EDS or EDX

Automated mineralogy and petrography are terms that refer to analytical solutions based on Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS or EDX). These systems can provide largely automated and quantitative analysis of minerals, rocks and manufactured materials.

Mineralogic

Petrolab offers automated mineralogy and petrography services using Mineralogic Mining, the automated mineral analysis system from Zeiss, with a Zeiss EVO MS 25 SEM and Bruker EDS detectors. Mineralogic enables the automatic detection, investigation and characterisation of particles of interest. We offer different levels of service depending on the requirements of the project. Please contact us for a current price list or to discuss your project and request a specific quotation.

Typical Uses

  • Reporting of modal mineralogy
  • Liberation yield: either wt. % particle (gravity applications) or % free perimeter (flotation applications)
  • Mineral locking and association
  • Particle and grain size distribution
  • Bright phase search (e.g. gold)
  • Ore and gangue characterisation
  • Regular auditing of processing circuits
  • Problem solving for mineral processing
  • Deportment of the target metal(s)

Advantages of Mineralogic

  • Fully quantitative EDS, minimising the requirement for microprobe or XRD
  • Classification schemes can be developed for individual mines, suitable for regular auditing work.
  • Fast analysis speeds using BSE greyscale mineral classification.
  • Mineral maps provide detailed compositional, textural and spatial distribution of target phases.

Petrolab Case Studies

Illustrating some of the analytical capabilities and potential applications for Mineralogic

The following example case studies have been assembled to demonstrate the mineralogical/petrological information that Petrolab can supply using Mineralogic – a product for automated mineral characterisation based on a Zeiss scanning electron microscope with integrated Bruker EDX detectors.

Case Study 1 - Liberation & association

Scope

The following data were obtained from the analysis of three sized fractions of a Pb-Zn metallurgical test sample (flotation feed) prepared as polished blocks. The project required information of mineralogical distribution of the target metals, liberation and mineral associations.

Analysis summary

Delineating grains into different phase classes is achieved by matching criteria that compare the quantitative measurements of elemental composition, as determined from the ED spectrum, with standard mineral composition data. Modal abundance data is reported in terms of weight percent. However, all data acquired are from 2D sections of 3D particles. Mass values are derived from measurement of particle / grain areas (with no correction for stereological error) and an assumed phase density. Abundance, grain size distribution and detailed liberation and association data for key phases from the Mineralogic liberation analysis can be determined. Several thousand particles can be analysed in a single analytical run providing a comprehensive dataset for an individual project. For this project, nearly 8000 particles were measured with approximately 15,000 grains analysed by EDS.

Sample Flotation Feed

Abundance

Automated mineralogy can provide modal abundances of samples with cumulative grain size distributions across multiple size fractions (Figure 1, Table 1, Figure 2).
Flotation Feed
Figure 1: Summary of mineral abundance for the flotation feed sample

Table 1: Abundance (by mass) for the Flotation Feed sample
Phase | s.g.¹
Combined (derived) 
-125+75 µm
-75+53 µm
53 µm
Fraction
%Sample
Fraction
%Sample
Fraction
%Sample
Galena | sg~7.40
48.5% 
52.4% 
30.3 
44.9% 
48.2 
52.2% 
21.5 
Sphalerite | sg~4.05
41.6% 
41.3% 
27.8 
42.8% 
53.5 
38.8% 
18.7 
Pyrite | sg~4.97
4.8% 
3.9% 
22.8 
5.2% 
56.7 
4.9% 
20.5 
Fe oxides | sg~5.30
2.2% 
1.2% 
15.5 
2.7% 
63.5 
2.3% 
21 
Silicate gangue | sg~2.61
1.9% 
0.6% 
9.3 
3.1% 
84.4 
0.6% 
6.3 
Jarosite | sg~3.09
0.3% 
0.2% 
15.7 
0.4% 
76.3 
0.1% 
Carbonate gangue | sg~2.71
0.3% 
0.1% 
5.7 
0.3% 
55.6 
0.6% 
38.6 
Baryte | sg~4.48
0.1% 
— 
— 
0.2% 
99.9 
0.0% 
0.1 
Chalcopyrite | sg~4.19
0.1% 
0.0% 
6.7 
0.1% 
56.1 
0.2% 
37.3 
Accessory min.† | sg~4.41
0.1% 
0.1% 
29.7 
0.1% 
36.8 
0.2% 
33.5 
Unclassified | sg~2.69
0.2% 
0.1% 
22.4 
0.2% 
62.8 
0.1% 
14.8 
¹ Abundance by mass calculated from measured phase area using average mineral s.g. data (webmineral.com or as otherwise estimated). A value of 0.0 indicates the phase was detected in the sample/fraction but with an abundance < 0.1. – – Indicates phase not detected in the sample/fraction. † Accessory minerals are other identified phases with a measured abundance less than 0.2%: Zn oxide · Smithsonite · Native silver

Size distribution

Automated analysis can provide information on the grain size distribution of the target elements (Figure 2).
AMCS2-B0

Figure 2: Cumulative grain size distribution for the flotation feed sample

Details sphalerite and galena association

The bar graphs & tables below provide a detailed breakdown by sample / fraction of the binary mineral associations for the target phase. The solo (green) and ternary (red) totals are also displayed at the bottom and top of each bar. A breakdown of ternary locking associations can be provided to allow calculation of the total locking association (binary + ternary) of an associate phase with the target phase.

Figure 3: Sphalerite association (detailed) for the flotation feed sample

 

Table 2: Sphalerite association (detailed) for the Flotation Feed sample
Phase association¹
Combined (derived) 
-125+75 µm
-75+53 µm
53 µm
Fraction
%Sample
Fraction
%Sample
Fraction
%Sample
Solo Sphalerite
80.6 
82.0 
28.5 
80.0 
51.6 
80.2 
19.9 
Binary: Galena
3.9 
6.0 
42.9 
1.3 
17.2 
7.8 
39.9 
Binary: Unclassified
3.7 
4.1 
31.2 
2.8 
39.3 
5.5 
29.5 
Binary: Silicate gangue
2.2 
4.3 
53.9 
2.0 
46.1 
0.0 
0.0 
Binary: Fe oxides
0.8 
0.1 
2.7 
0.8 
52.2 
1.9 
45.1 
Binary: Accessory min.†
0.4 
0.2 
16.1 
0.2 
23.3 
1.1 
60.5 
Binary: Pyrite
0.2 
0.2 
18.0 
0.1 
15.8 
0.8 
66.2 
Binary: Carbonate gangue
0.1 
— 
— 
0.1 
97.6 
0.0 
2.4 
Binary: Chalcopyrite
0.0 
0.1 
100.0 
— 
— 
— 
— 
Binary: Jarosite
0.0 
— 
— 
0.0 
69.3 
0.0 
30.7 
Ternary+ Sphalerite
4.4 
3.1 
46.6 
12.8 
82.5 
2.7 
6.8 
¹ Association by proportion of the total mineral mass of the associator (target) phase. A value of 0.0% indicates the associate phase was detected in the sample/fraction but was associated with < 0.1% of the total associator phase mass, whereas – – indicates the associate phase was not detected in a particular sample/fraction. † Accessory minerals are other identified phases with a measured abundance less than 0.2% (see Abundance).

Galena association (detailed) for the Flotation Feed sample

Figure 4: Galena association (detailed) for the flotation feed sample.

Table 3: Galena association (detailed) for the Flotation Feed sample
Phase association¹
Combined
(derived) 
-125+75 µm
-75+53 µm
53 µm
Fraction
%Sample
Fraction
%Sample
Fraction
%Sample
Solo Galena
71.3 
71.9 
28.2 
67.6 
49.3 
80.0 
22.5 
Binary: Fe oxides
3.8 
3.2 
23.5 
2.7 
37.5 
7.3 
39.0 
Binary: Silicate gangue
3.0 
6.5 
61.4 
1.9 
32.7 
0.9 
5.9 
Binary: Accessory min.†
2.0 
2.9 
40.9 
1.8 
46.2 
1.3 
12.9 
Binary: Sphalerite
1.7 
4.2 
69.0 
0.7 
21.2 
0.8 
9.8 
Binary: Unclassified
1.5 
0.9 
16.7 
0.7 
24.1 
4.4 
59.1 
Binary: Pyrite
0.7 
1.6 
63.1 
0.4 
30.0 
0.2 
6.9 
Binary: Jarosite
0.4 
0.3 
25.4 
0.4 
49.2 
0.5 
25.4 
Binary: Carbonate gangue
0.0 
— 
— 
— 
— 
0.0 
100.0 
Ternary+ Galena
15.7 
8.5 
15.2 
23.9 
79.2 
4.5 
5.7 
¹ Association by proportion of the total mineral mass of the associator (target) phase. A value of 0.0% indicates the
associate phase was detected in the sample/fraction but was associated with < 0.1% of the total associator phase
mass, whereas – – indicates the associate phase was not detected in a particular sample/fraction.
† Accessory minerals are other identified phases with a measured abundance less than 0.2% (see Abundance).

Sphalerite and galena liberation yield

The cumulative liberation yield curve (grade-recovery curve) provides a mineralogically limited representation of liberation (Figures 5 and 6). Each particle is assigned to a liberation class depending on the ‘grade’ of the particle. Particle grade for flotation samples, as in this example, is determined from the percentage of the perimeter of a particle shared with the free perimeter of the target phase (as measured in 2D section). For gravity separation applications, the particle grade is usually determined from the percentage of the particle area occupied by the target phase (as measured in 2D section). For either measurement of particle grade, the total mineral mass in each liberation class (the liberation yield) is determined and the cumulative curve is plotted by summing the individual class liberation yield with all higher classes.
The cumulative liberation yield curve represents the theoretical maximum mineral recovery at each particle grade class and does not reflect any other recovery factors that could affect the metallurgical process. The percentage of each sample fraction that is ‘liberated’ (value for each fraction in bold in the table below the graph) is calculated in this report from the cumulative mineral mass of a phase in all particles with an apparent grade of > 80%. Other values reported can include ‘locked’ (0 < 40% particle grade) and ‘middlings’ (40 < 80% particle grade).

AMCS2-B0_CaseStudy2_Liberation_Web_htm_m7ebda8cb

 

Galena cumulative liberation yield

 

Figure 6: Galena cumulative liberation yield for the Flotation Feed fractions