DIAMOND 



25 



prism, and so on with other gems. For want of a knowledge of the crystalline form 

 of the diamond a gentleman in California offered 2QQI. for a small specimen of quartz. 

 He knew nothing of the substance, except that it was a bright, shining mineral, exces- 

 sively hard, not to be scratched by the file, and which would scratch glass. Pre- 

 suming that these qualities belonged only to the diamond, he conceived that he was 

 offering a fair price for the gem ; but the owner declined the offer. Had he known 

 that the diamond was never found as a six-sided prism, terminated at each end by a 

 six-sided pyramid, he would have been able to detect the fact that what he was offered 

 200/. for, was really not worth more than half-a-crown.' Tennanfs Lecture on Gems. 

 The accompanying forms (Jigs. 605 and 606) may serve to guide those who are 

 ignorant of crystallography : 



607 Brilliant (upper side). 608 Eose. 



605 



e 100 

 carets 



Diamond. 



o 



o, table ; 5, star-facets ; e, skill-facets ; rf, lozenges ; e , girdle. 



The following technical terms are applied to the different faces of diamonds : 



Bezils : the upper sides and corners of the brilliant* lying between the edge of the 

 table and the girdle. 



Collet : the small horizontal plane or face, at the bottom of the brilliant. 



Crown : the upper work of the rose, which all centres in the point at the top, and is 

 bounded by the horizontal ribs. 



Facets : small triangular faces or planes, both in brilliants and roses. In brilliants 

 there are two sorts, skew- or skill-facets, and star-facets. Skill-facets are divided into 

 upper and under. Upper skill-facets are wrought on the lower part of the bezil, and 

 terminate in the girdle ; under skill-facets are wrought on the pavilions, and terminate 

 in the girdle ; star-facets are wrought on the upper part of the bezil, and terminate in 

 the table. 



Girdle : the line which encompasses the stone parallel to the horizon ; or, which 

 determines the greatest horizontal expansion of the stone. 



Lozenges : are common to brilliants and roses. In brilliants they are formed by the 

 meeting of the skill- and star-facets on the bezil. In roses by the meeting of the facets 

 in the horizontal ribs of the crown. 



Pavilions : the under sides and corners of brilliants, lying between the girdle and 

 the collet. 



Ribs : the lines or ridges, which distinguish the several parts of the work, both in 

 brilliants and roses. 



Table : the large horizontal plane, or face, at the top of the brilliant. 



Fig. 607 represents a brilliant, and^. 608 a rose-cut diamond. 



The rose-diamond is flat beneath, like all weak stones, while the upper face rises 

 into a dome and is cut into facets. Most usually six facets are put on the central 

 region which are in the form of triangles, and unite at their summits ; their bases 

 abut upon another range of triangles, which being set in an inverse position to the 

 preceding, present their bases to them, while their summits terminate at the sharp 

 margin of the stone. The latter triangles leave spaces between them which are like- 

 wise cut each into two facets. By this distribution the rose-diamond is cut into 2-t 

 facets ; the surface of the diamond being divided into two portions, of which the upper 

 is called the crown, and that forming the contour, beneath the former, is called dentelle 

 (lace) by the French artists. 



According to Mr. Jefferies, in his ' Treatise on Diamonds,' the regular rose-diamond 

 is formed by inscribing a regular octagon in the centre of the table side of the stone, 

 and bordering it by eight right-angled triangles, the bases of which correspond with 

 the sides of the- octagon ; beyond these is a chain of 8 trapeziums, and another of 

 16 triangles. The collet side also consists of a minute central octagon, from every 

 angle of which proceeds a ray to the edge of the girdle, forming the whole surface 



