and youl fo anmber of cat So, ao NAl,Os etc). To calculate a mineral formula uni

Question

and youl fo anmber of cat So, ao NAl,Os etc). To calculate a mineral formula unit of anioa (Forsterite content) of olivine analyses Please make sure that your writing is legible It is often convenient to be able to determine to know the number of cations per 4 oxygens. below for converting oxide weight percents to need to determine the number of Mg and will lose points miner electron m For example, to calculate chemistry of eiven as oxide weight percents (e.g. SiO,, Cao, Na, a mineral can be analyzed with an need to know the number of cations per the cations present in an olivine grain, you See the example in Table 1 and the instructions number of cations. To calculate the Fo content, you n Fe cations per 4 oxygens o llat the instructn er o Cations on basis of 4 0.989 0.870 0.012 1.140 Example: Table 1 6009-Proportion #cations-Oxygens 1.85 70.94 Weeh1% Molecular weights" / Molecular . , Y.-3d% 34.96 36.77 0581790.58179 0.58179 1.1636 0.52 70.34 t-0.51176 T 0.511761051176 0.00733 | 0.00733 | 0.00733 Foo, Feo Mno Mgo 27.04 99.29 0.6780 0.6780 2.3535 Total 40.31 0.67800 1. The electron probe data for the oxides are reported in Weight The above analysis shows that the analyzed olivine has 34.96 wt. %sos 2 To calculate the Molecular Proportion (that is, the number of MOLES weight % by the molecular weight of SiO2 (or Feo, etc.). Use the following ES of SiO2 etc.), divide weights. Sio,-60.09, Fe0: 71.85. MnO-70.94, MgO 40.31. 3. The # Cations in this olivine refers to the number of moles of each cation (siin sio2 for example). Because all of the cations in t moles of O, the number of cations and the molecular proportions are equal. If Al:O, were present in this analysis, then the number of cations would be twice the molecular proportion (e.g, there are 2 moles of Al in Al O,). his example are present as 1 mole of cation per xx 4. determine the number of cations of O, for Sio, because there are 2 O in Si0,). the same a The # Oxygens refers to the number of moles of O in each oxide (2 moles of O . All others are the same as the molecular proportion multiply the molecular proportion by 2 (because, for example, there is only one mole of O in Feo), in SiO2). To

Explanation / Answer

calculation mentioned below

(Fo) % = 0.75045/1.20826 x 100 = 38.3 %

Mineral Olivine (Mg++,Fe++)2 Sio4

Foesterite content = 38.3

Oxides Weight % Moleculer weight % Moleculer proportion Cation Oxygen cation on basis of 4 O Sio2 33.6 60.09 0.55916 0.55916 1.1182 1.00089 Feo 48.5 71.85 0.67501 0.67501 0.67501 1.20826 Mno 1.20 70.94 0.01691 0.01691 0.01691 0.03026 Mgo 16.9 40.31 0.41925 0.41925 0.41925 0.75045 Total 100.2 2.22937

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