STUDENT A

Read the text and ask student B questions to complete the spaces. Then answer student B's questions.

RUBY[17]

The ruby is a 1............................ to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). The red color is caused mainly by the presence of the element 3............................Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called 5............................. The ruby is considered one of the four precious stones, together with the sapphire, the emerald, and the diamond.

Prices of rubies are primarily determined by 7............................. The brightest and most valuable "red" called pigeon blood-red, commands a huge premium over other rubies of similar quality. After color follows 9............................ : similarly to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Cut and carat (weight) also determine the price.

STUDENT B

Read the text and answer student A's questions. Then ask student A questions to complete the spaces.

RUBY[17]

The ruby is a pink to blood-red colored gemstone, a variety of the mineral 2............................ (aluminium oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for 4............................. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the 6............................, and the diamond.

Prices of rubies are primarily determined by color. The brightest and most valuable "red" called 8............................, commands a huge premium over other rubies of similar quality. After color follows clarity: similarly to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Cut and 10............................ (weight) also determine the price.

Read the article and fill the gaps with appropriate words.

RUBY: PHYSICAL PROPERTIES[17]
 

gems
luminescence octahedrally crystallographic
white harder scale corundum
Al2O3 laser absorbed  
chromium3+ region mirrors  
luster effect stimulated  


Rubies have a hardness of 9.0 on the Mohs 1............................ of mineral hardness. Among the natural 2............................ only moissanite and diamond are 3............................ , with diamond having a Mohs hardness of 10.0 and moissonite falling somewhere in between 4............................ (ruby) and diamond in hardness. Ruby is alfa-alumina (the most stable form of 5............................) in which a small fraction of the aluminum3+ ions are replaced by 6............................ ions. Each Cr3+ is surrounded 7............................ by six O2- ions. This 8............................ arrangement strongly affects each Cr3+, resulting in light absorption in the yellow-green 9............................ of the spectrum and thus in the red color of the gem. When yellow-green light is 10............................ by Cr3+, it is re-emitted as red 11............................ . This red emission adds to the red colour perceived by the subtraction of green and violet light from 12............................ light, and adds 13............................ to the gem's appearance. When the optical arrangement is such that the emission is 14............................ by 694-nanometer photons reflecting back and forth between two 15............................, the emission grows strongly in intensity. This 16............................ was used by Theodore Maiman in 1960 to make the first successful 17............................, based on ruby.