Chap. 54.] ACHATES. 439 



of Berenice. It is partly composed of crystal, arid hence it is 

 that some have called it " root of crystal." It takes its name 

 14 iris" from the properties which it possesses; for, when, 

 struck by the rays of the sun in a covered spot, it projects upon 

 the nearest walls the form and diversified colours of the rain- 

 how ; continually changing its tints, and exciting admiration 

 by the great variety of colours which it presents. That it is 

 hexahedral in form, like crystal, is generally agreed; but some 

 say that it is rough on the sides and of unequal angles; 

 and that, when exposed to a full sun, it disperses the rays 

 that are thrown upon it, while at the same time, by throw- 

 ing out a certain brightness 16 before it, it illumines all ob- 

 jects that may happen to be adjacent. The stone, however, 

 as already stated, only presents these colours when under 

 cover ; not as though they were in the body of the stone 

 itself, but, to all appearance, as if they were the result of the 

 reflected light upon the surface of the wall. The best kind is 

 the one that produces the largest arcs, with the closest resem- 

 blance to the rainbow. 



" Iritis*' is the name of another stone, similar to the last in 

 all other respects, but remarkable for its extreme hardness. 

 Horua says, in his writings, that this stone, calcined and tritu- 

 rated, is a remedy for the bite of the ichneumon, and that it is 

 a native of Persia. 



CHAP. 53. LEIIOS. 



The stone called "leros" 17 is similar in appearance, but does 

 not produce the same effects. It is a crystal, with streaks of 

 white and black running across it. 



CHAP. 54. ACHATKS; THE SEVERAL VARIETIES OF IT. ACOPOS ; 



THE KKMKDIKM PKKIVKP FKOM IT. ALA1IASTIUTXS ; THE Rl> 

 MmiKS DKK1VK1) FROM IT. ALKCTORIA. ANDIiODAMAS. AU- 

 CYKODAMAS. ANill'ATlIKS. AUAHICA. AKOMATIT1S. ASHESTOS. 

 ABI'ISATIS. ATI/OK. AUGKT1S. AMl'JIIDANES OR CHKYSOCOLLA. 

 APIIliODISlACA. AI'SYCTOS. JKGYPT1LLA. 



Having now described the principal precious stones, classified 



quartz iridizcd internally, or prismatic crystals of Limpid quartz, xvhich 

 decompose tin; rays of the sun. 



f c Ihc reading and Tin-fining of this passage are very doubtful. 



17 TLo reading is doubtful, zeros " and *' trros " being given by some 

 MSS. AjdFsoii hazard* a conjecture that it may have been a variety of 

 quartz, formed of u concretion of agates united by a cement of a similar 

 Laturc. 



