For a mineral . `LiAl (SiO_3)_2`, what is the charge on `SiO_3` unit ?
What is the arrangement of oxygen atoms around the silicon atom ?

Explanation

To solve the problem regarding the mineral `LiAl(SiO3)2`, we need to determine the charge on the `SiO3` unit and the arrangement of oxygen atoms around the silicon atom. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the charges of the cations
1. **Lithium (Li)** has a charge of +1.
2. **Aluminium (Al)** has a charge of +3.

### Step 2: Set up the equation for the overall charge
The formula for the mineral is `LiAl(SiO3)2`, which means it contains:
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