Fusion (melting) temperature of high-purity silica (SiO2): choose the closest standard value in °C used in refractory practice.

Introduction / Context:
The fusion temperature of silica is a core reference when selecting acidic refractories for roofs, checkerwork, and coke-oven walls. Pure silica exhibits a high melting point and complex polymorphic behavior that influences thermal expansion and spalling resistance.

Given Data / Assumptions:

• Purity refers to high-SiO2 compositions with minimal fluxing impurities.
• Standard melting value for quartz/silica used in handbooks is required.

Concept / Approach:
Silica (SiO2) has a melting (fusion) point around 1710–1715 °C. The exact figure depends slightly on crystalline form and measurement conditions, but 1715 °C is widely cited in refractory practice and materials texts.

Step-by-Step Solution:

Verification / Alternative check:
Vendor datasheets for silica bricks list softening and transformation ranges below fusion; fusion reference is consistently ~1715 °C for pure SiO2.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing softening under load with fusion; ignoring the role of impurities that can flux silica at lower temperatures.

Final Answer:
1715 °C