354 THE DIAMOND AND OTHER PRECIOUS STONES. 



avoiding- a large rellectiiig upper surface, the stoue is made to exTiibit 

 its fundameutal color throughout its whole extent. The emerald, though 

 much cheaper than the beautiful ruby, is nevertheless much admired 

 and sough*: for. We might almost call it a " stone of general alfection," 

 so nuich is it esteemed by the many. 



The scf])phire, which comes after the emerald, is the hardest of colored 

 stones. It may be considered as a blue ruby, or the ruby as a red 

 sapphire. With naiiy and Mawe, we can say that aluminium is suscepti- 

 ble of crystallizing in almost all colors. The mineralogical species to 

 which the sapphire belongs is called the corindon. After the red corin- 

 don, or oriental riihy, comes the blue corindon., or oriental sapphire. Some- 

 times the corindon is of a beautiful yellovr color ; then it is called oriental 

 topas. More rarely it is of a violet hue; then it takes the name of orien- 

 tal amethyst. Finally, it may be perfectly colorless, like rock-crystal, 

 when it greatly resembles the diamond, with which it is sometimes con- 

 founded, but by its greater weight and its double refraction it may be 

 easily distinguished. 



By the microscope there may be discovered, in certain pale sapphires, 

 traces in the direction of the faces of sis-sided prisms. The light re- 

 flected by these internal filaments produces three small briUiant traces 

 transversely to the filaments and to the faces of the prism. The cross- 

 ing of these little bright lines forms within the stone a six-pointed star, 

 which gives to the stone the name of starry sapphire. Among the ori- 

 entals these stones are highly esteemed, especially when they exhibit 

 the star in a ground of deep blue. Corindons of all colors are suscepti- 

 ble of being thus marked. In his voyages in Africa, M. Abbadie wore 

 a blue starry sapphire, which often commanded the respect of the 

 natives. There are stars on a red, blue, or yellow ground, accordin g to 

 the color of the corindon. As yet, this phenomenon has never been 

 seen in the white sapphire. I have just said that this reflection arises 

 from little filaments within the stone. These may result either from 

 some foreign substance or from minute hollows left by the regular dis- 

 position of the particles at the moment of crystallization. If, instead of 

 trying to observe these starry appearances by reflectiou, the stone is cut 

 so that it can be looked through, then the phenomenon can be easily 

 seen. Unless the stone is of a very perfect crystallization, the observer 

 who takes for the point of sight a lighted candle, placed at a moderate dis- 

 tance, will perceive these little luminous lines of light crossing all the 

 series of filaments which the mineral contains. According as the stone 

 has a four or six sided form, we have a four or six rayed star, and if the 

 filaments are all in one direction we have a luminous band. 



In scratching with the point of a diamond a plate of glass in various 

 directions, we produce bands of light of the same number as the traces 

 ui^on the surface, which are always in a transverse direction to these 

 traces. We can even very simj^ly produce a star in spreading with the 

 finger a little wax or grease upon a plate of thin glass. It is necessary 



