Question 5. 1) The following raw microprobe data was obtained from the microprob
ID: 1031299 • Letter: Q
Question
Question 5. 1) The following raw microprobe data was obtained from the microprobe analysis of four common sulphide minerals. Calculate the mineral formula in each case (showing calculations) and, take into account possible elemental substitutions, name the minerals (refer to mindat.org). The number of atoms for each calculation is shown below each analysis 2) Comment on the possible economic and environmental significance of these minerals, including trace or minor elements in some of the analyses. 2 Wt% 7.99 4 Wt% 1.53 43.10 19.16 Fe Ni Cd Co Cu Ag Zn Sb As 1.23 4.05 35.4 5.67 3.98 26.6 2.08 24.0 99.2 6.07 67.95 57.38 5.15 3.88 16.37 99.42 33.58 99.89 32.99 99.36 Total (Atoms) 17 29 2 29Explanation / Answer
Q) 5
1) No of atoms = ( weight %/ 100 x total mass)/molar mass
Fe atom = ((43.10/100)x (total number of atoms x molar mass of Fe))/ Molar mass
=((43.10/100)x (55.847 x17))/ 55.847
= 7.327
Total number of Fe atom is 7
Ni atom = ((19.16/100)x (total number of atoms x molar mass of Ni))/ Molar mass
=((19.16/100)x (58.6934x17))/ 58.6934
= 3.2572
Total number of Ni atom is 3
Co atom = ((19.16/100)x (total number of atoms x molar mass of Co))/ Molar mass
=((19.16/100)x (58.933195 x17))/ 58.933195
= 0.6 =1
Total number of Co atom is 1
S atom = ((33.58/100)x (total number of atoms x molar mass of S))/ Molar mass
=((33.58/100)x (32.065 x17))/ 32.065
= 5.7 =6
Total number of S atom is 6
Mineral formula for 1 is Fe7S6Ni3Co
ii)
Cu atom = ((6.07/100)x (total number of atoms x molar mass of Cu))/ Molar mass
=((6.07/100)x (63.546 x29))/ 63.546
= 1.5782 =2
Total number of Cu atom is 2
Ag atom = ((67.95/100)x (total number of atoms x molar mass of Ag))/ Molar mass
=((67.95/100)x (107.8682 x29))/ 107.8682
= 19.70=20
Total number of Ag atom is 20
Sb atom = ((5.15/100)x (total number of atoms x molar mass of Sb))/ Molar mass
=((5.15/100)x (121.76 x29))/ 121.76
= 1.4935 = 2
Total number of Sb atom is 2
S atom = ((16.37/100)x (total number of atoms x molar mass of S))/ Molar mass
=((16.37/100)x (32.065 x29))/ 32.065
= 4.7473 = 5
Total number of S atom is 5
Mineral formula for 2 is Ag20S5Cu2Sb2. (As is present as a trace element)
iii)
Fe atom = ((7.99/100)x (total number of atoms x molar mass of Fe))/ Molar mass
=((7.99/100)x (55.847 x2))/ 55.847
= 0.1598
Total number of Fe atom is trace.
Cd atom = ((1.23/100)x (total number of atoms x molar mass of Cd))/ Molar mass
=((1.23/100)x (112.411 x2))/ 112.411
= 0.0246
Total number of Cd atom is trace.
Zn atom = ((57.38/100)x (total number of atoms x molar mass of Zn))/ Molar mass
=((57.38/100)x (65.38 x2))/ 65.38
= 1.1476
Total number of Zn atom is =1
S atom = ((32.99/100)x (total number of atoms x molar mass of S))/ Molar mass
=((32.99/100)x (32.065 x2))/ 32.065
= 0.6598 =1
Total number of S atom is 1
Mineral formula for 3 is ZnS and Cd and Fe is present as trace amount.
iv)
Fe atom = ((1.53/100)x (total number of atoms x molar mass of Fe))/ Molar mass
=((1.53/100)x (55.847 x29))/ 55.847
= 0.4437
Total number of Fe atom is trace
Cu atom = ((35.4/100)x (total number of atoms x molar mass of Cu))/ Molar mass
=((35.4/100)x (63.546 x29))/ 63.546
= 10.266
Total number of Cu atom is 10
Ag atom = ((5.67/100)x (total number of atoms x molar mass of Ag))/ Molar mass
=((5.67100)x (107.8682 x29))/ 107.8682
= 1.6443
Total number of Ag atom is 2
Zn atom = ((3.98/100)x (total number of atoms x molar mass of Zn))/ Molar mass
=((3.98/100)x (65.38 x29))/ 65.38
= 1.1542
Total number of Zn atom is =1
Sb atom = ((26.6/100)x (total number of atoms x molar mass of Sb))/ Molar mass
=((26.6/100)x (121.76 x29))/ 121.76
= 7.714
Total number of Sb atom is 8
As atom = ((2.08/100)x (total number of atoms x molar mass of As))/ Molar mass
=((2.08/100)x (74.9216 x29))/ 74.9216
= 0.6 =1
Total number of As atom is 1
S atom = ((24.0/100)x (total number of atoms x molar mass of S))/ Molar mass
=((24.0/100)x (32.065 x29))/ 32.065
= 6.96
Total number of S atom is 7
Mineral formula for 4 is Cu10Sb8S7Ag2Zn1As1 ( here Fe is present as a trace element )
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