1. The crystal cup is also a kind of glass, and its main component is also silicon dioxide, but substances such as lead, barium, zinc and titanium are introduced into it. Because this kind of glass has high transparency and refractive index, its appearance is bright and clean, so it is called crystal glass.

2. The thermal conductivity of crystal is stronger than that of glass, so it should be cooler when touching the crystal with hands than touching the glass.

3. Look at the hardness. Rock crystal hardness is 7, and glass hardness is 5, so crystal can carve glass.

4. Look at the refraction. Lift a crystal cup and spin it against the light, and you will find that it is just like a beautiful handicraft, white and transparent, reflecting the charming colorful light, because crystal can absorb luster and even ultraviolet rays, while ordinary glassware has no luster and no refraction.

5. Listen to the sound. When you tap lightly or flick with your fingers, crystal glassware can make a light and brittle metallic sound, and ripple a beautiful aftersound when you wear air, while ordinary glassware only has a dull "click, click" sound.