**Core Concept**
Leucite ceramics are a type of dental restorative material used for crowns, bridges, and implants. They are composed of a mixture of leucite crystals, a glass matrix, and other additives. The unique properties of leucite ceramics make them an attractive option for dental restorations.

**Why the Correct Answer is Right**
Leucite ceramics exhibit excellent mechanical properties, including high strength, hardness, and durability. The leucite crystals are responsible for these properties, as they provide a high degree of resistance to wear and tear. Additionally, leucite ceramics are biocompatible and can be easily polished, making them an ideal choice for dental restorations. The glass matrix helps to bind the leucite crystals together, providing a strong and durable bond.

**Why Each Wrong Option is Incorrect**
**Option A:** Leucite ceramics are not made from a mixture of quartz and glass.
**Option B:** The primary component of leucite ceramics is not feldspar, but rather leucite crystals.
**Option C:** Leucite ceramics do not have a high coefficient of thermal expansion, which actually makes them more suitable for dental restorations.

**Clinical Pearl / High-Yield Fact**
When considering dental restorations, it's essential to choose materials that are both durable and biocompatible. Leucite ceramics meet both of these criteria, making them a popular choice among dentists.

**Correct Answer:** C.