Question

Commonly occurring feldspars illustrated in the following formulas. A. $Al_2O_3 \cdot 2H_2O \cdot 6SiO_2$
B. $CO \cdot Al_2O_3 \cdot 2SiO_2$
C. $K_2O \cdot Al_2O_3 \cdot 6SiO_2$
D. $Na_2O \cdot Al_2O_3 \cdot 6SiO_2$
E. $CaO \cdot Al_2O_3 \cdot 2SiO_2$

• A. C, E and D Only
• B. A, C and E Only
• C. B, E and D Only
• D. E, D and A Only

Hint:

Logic Tip: Feldspars are mainly potassium, sodium, or calcium alumino-silicates.

Answer 1

The Correct Option is A

Concept:
Feldspars are important flux-bearing minerals used in ceramic bodies and glazes. Common feldspars mainly contain:
• Potassium
• Sodium
• Calcium
•

Step 1:
The formula: \[ K_2O \cdot Al_2O_3 \cdot 6SiO_2 \] represents potassium feldspar. Thus: \[ C \text{ is correct} \]
•

Step 2:
The formula: \[ Na_2O \cdot Al_2O_3 \cdot 6SiO_2 \] represents sodium feldspar. Thus: \[ D \text{ is correct} \]
•

Step 3:
The formula: \[ CaO \cdot Al_2O_3 \cdot 2SiO_2 \] represents calcium feldspar. Thus: \[ E \text{ is correct} \]
•

Step 4:
Option A represents kaolin-type composition while option B is not a standard feldspar formula. \[ \boxed{\text{(1) C, E and D Only}} \]