The anion, `(Si_(6)O_(18))^(12-)` is present in

Options

A. pyroxene
B. beryl
C. mica
D. albite

Answer

To determine where the anion \((Si_6O_{18})^{12-}\) is present, we can follow these steps:

### Step 1: Understand the Structure of the Anion
The anion \((Si_6O_{18})^{12-}\) represents a silicate structure. It consists of 6 silicon (Si) atoms and 18 oxygen (O) atoms. This structure can be visualized as a cyclic or ring silicate, where the tetrahedral units of silicon are interconnected through shared oxygen atoms.

**Hint:** Look for silicate structures that involve multiple silicon and oxygen atoms, particularly those that form rings.

### Step 2: Identify the General Formula
The general formula for this type of silicate can be expressed as \(SiO_3\) with a variable \(N\), where \(N\) represents the number of tetrahedral units. For the anion in question, we can deduce that \(N = 6\) since there are 6 silicon atoms.

**Hint:** Recognize that the formula \(SiO_3\) can be scaled by the number of tetrahedral units in the structure.

### Step 3: Relate to Known Silicate Minerals
The anion \((Si_6O_{18})^{12-}\) is characteristic of certain silicate minerals. One notable example is Beryl, which is an aluminosilicate mineral. The formula for Beryl is \(Be_3Al_2Si_6O_{18}\), indicating the presence of the silicate ring structure.

**Hint:** Recall common silicate minerals and their formulas to find a match for the given anion.

### Step 4: Conclusion
Based on the analysis, the anion \((Si_6O_{18})^{12-}\) is present in the mineral Beryl. Beryl is known for its hexagonal crystal structure and is a significant source of beryllium.

**Hint:** Confirm your findings by checking the mineral composition and structure of Beryl.

### Final Answer
The anion \((Si_6O_{18})^{12-}\) is present in Beryl.