How many of the following are the minerals of aluminimum?
Magnesite, cryolite, kaolinite, malachite, epsum salt, bauxite, cuprite

Answer

To determine how many of the given substances are minerals of aluminum, we will analyze each one individually.

1. **Magnesite (MgCO3)**:
- Magnesite is an ore of magnesium, not aluminum.
- **Conclusion**: Not a mineral of aluminum.

2. **Cryolite (Na3AlF6)**:
- Cryolite is known to be an ore of aluminum. It contains aluminum in its chemical formula.
- **Conclusion**: This is a mineral of aluminum.

3. **Kaolinite (Al2Si2O5(OH)4)**:
- Kaolinite is also an ore of aluminum. It contains aluminum in its structure.
- **Conclusion**: This is a mineral of aluminum.

4. **Malachite (Cu2CO3(OH)2)**:
- Malachite is an ore of copper, not aluminum.
- **Conclusion**: Not a mineral of aluminum.

5. **Epsom Salt (MgSO4·7H2O)**:
- Epsom salt is an ore of magnesium and does not contain aluminum.
- **Conclusion**: Not a mineral of aluminum.

6. **Bauxite (Al2O3·2H2O)**:
- Bauxite is the primary ore of aluminum and contains aluminum in its composition.
- **Conclusion**: This is a mineral of aluminum.

7. **Cuprite (Cu2O)**:
- Cuprite is an ore of copper and does not contain aluminum.
- **Conclusion**: Not a mineral of aluminum.

Now, let's summarize the minerals of aluminum identified:

- Cryolite
- Kaolinite
- Bauxite

Thus, the total number of minerals of aluminum from the given list is **3**.

### Final Answer:
**3**