Rocca di cristallo refers to:

• A. A glasslike material used in crystal glassware.
• B. A gemstone used for jewelry.
• C. A mineral used to make pigments.
• D. A rock crystal in Italian, which cristallo glass resembled.

Answer: (D)

Rocca di cristallo is about a name tied to appearance. Cristallo glass was designed to mimic the clear, colorless look of rock crystal, the natural mineral quartz. In Italian, cristallo signals this resemblance to rock crystal, so the term describes the glass’s intended optical quality, not an actual gemstone or a pigment or a generic glass material. The term emphasizes purity and sparkle by likening the glass to the natural crystal. So the correct interpretation is that cristallo glass resembled rock crystal in Italian.