Q 01/05

The word crystal comes from the Ancient Greek krustallos, which meant both 'rock crystal' and what?

A) Star

B) Glass

C) Ice

D) Salt

Answer · why

C) Ice

Greek philosophers including Theophrastus thought quartz was supercooled ice, an idea Pliny the Elder repeated and which lasted into the 17th century.

Q 02/05

Despite the name, lead crystal and crystal glass are actually what kind of solid?

A) Polycrystals

B) Quasicrystals

C) Amorphous solids

D) Single crystals

Answer · why

C) Amorphous solids

Glass has no periodic arrangement of atoms at all, unlike true crystals such as table salt or diamond.

Q 03/05

Crystal structures are grouped into how many crystal systems?

A) Four

B) Twelve

C) Seven

D) Fourteen

Answer · why

C) Seven

Halite's cubes belong to the cubic system, while ordinary water ice is hexagonal.

Q 04/05

Which symmetry can quasicrystals show that is impossible for an ordinary periodic crystal?

A) Two-fold

B) Three-fold

C) Five-fold

D) Six-fold

Answer · why

C) Five-fold

The holmium-magnesium-zinc quasicrystal can even grow as a pentagonal dodecahedron; the discovery forced crystallographers to redefine the word crysta...

Q 05/05

Quartz defines which value on the Mohs hardness scale?

A) 9

B) 8

C) 7

D) 10

Answer · why

C) 7

Its name comes from the German Quarz, ultimately from a Slavic word meaning 'hard'; it is a framework of silicon-oxygen tetrahedra with formula SiO2.