Among the following ores Bauxite, Siderite, Cuprite, Calamine, Haematite, Kaolinite, Malachite, Magnetite, Sphalerite, Limonite, Cryolite, the number of principal ores of iron is

We need to identify the principal ores of iron from the given list of ores.

Let us analyze each ore:

1. Bauxite ($$Al_2O_3 \cdot 2H_2O$$): Principal ore of Aluminium, not iron.

2. Siderite ($$FeCO_3$$): This is an ore of iron. $$\checkmark$$

3. Cuprite ($$Cu_2O$$): Principal ore of Copper, not iron.

4. Calamine ($$ZnCO_3$$): Principal ore of Zinc, not iron.

5. Haematite ($$Fe_2O_3$$): This is a principal ore of iron. $$\checkmark$$

6. Kaolinite ($$Al_2Si_2O_5(OH)_4$$): This is an ore of Aluminium (a clay mineral), not iron.

7. Malachite ($$Cu(OH)_2 \cdot CuCO_3$$): Principal ore of Copper, not iron.

8. Magnetite ($$Fe_3O_4$$): This is a principal ore of iron. $$\checkmark$$

9. Sphalerite ($$ZnS$$): Principal ore of Zinc, not iron.

10. Limonite ($$2Fe_2O_3 \cdot 3H_2O$$): This is an ore of iron. $$\checkmark$$

11. Cryolite ($$Na_3AlF_6$$): Used in extraction of Aluminium, not iron.

Iron ores identified: Siderite, Haematite, Magnetite, Limonite = 4

Hence, the answer is 4.