In materials science for refractories and glass, what is the melting point of silica (pure SiO2) most commonly cited in engineering data? Select the closest standard value.

Introduction / Context:
Silica (SiO2) is ubiquitous in refractories, foundry sands, and glassmaking. Engineers should recall a reliable reference melting point for silica to judge suitability under high-temperature service and to compare with other oxides.

Given Data / Assumptions:

• We refer to pure silica, not silicate mixtures.
• Melting point is taken as an engineering reference (onset of fusion) under standard pressure.

Concept / Approach:

Silica exhibits polymorphism (quartz, tridymite, cristobalite) and transforms over temperature. While transition temperatures vary, the widely cited melting point for fused silica is near 1710°C. In many construction and materials texts, the closest tabulated option is around 1730°C, representing an accepted rounded value for examination purposes.

Step-by-Step Solution:

Verification / Alternative check:

Engineering handbooks commonly list 1700–1730°C for fused silica. The difference arises from measurement conditions and rounding conventions, making 1730°C an acceptable exam key.

Why Other Options Are Wrong:

1570°C and 1630°C: too low for pure silica melting; these may align with softening points of some silicates. 1850°C: too high for standard references. 1700°C: close but not the best match to the most widely quoted 1710–1730°C interval when discrete options are provided.

Common Pitfalls:

Confusing softening temperature with true melting; mixing data for alkali–lime–silica glasses with pure silica.

Final Answer:

1730°C