200 ZIRCO-M.V. 



and to bear the same relation to ordinary chrysaberyl aa 

 emerald to beryl. 



Dif. Near beryl, but distinct in its often tabular crystal- 

 lizations, and its entire infusibility. 



Obs, Chrysoberyl occurs in the United States in granite 

 at Haddam, Conn., and Greenfield, near Saratoga, N. Y., 

 associated with beryl, garnet, etc. 



The name chrysoberyl is from the Greek chrysos, golden, 

 and beryllos, beryl. Cymophane is another name of the 

 species, alluding to its opalescence, and derived from the 

 Greek kuma, wave, and phaino, to appear. 



Uses, The crystals are seldom sufficiently pellucid and 

 clear from flaws to be valued in jewelry ; but when of fine 

 quality, it forms a beautiful gem, and is often opalescent. 



Phenacite. Colorless or bright wine-yellow, inclining to red, of 

 vitreous luster and transparent to opaque. Crystals and cleavage rhom- 

 bohedral. H=8. Gr=297. Composition, silica 54*3, glucina 45 - 7, 

 with a trace of magnesia and alumina. Unaltered before the blowpipe. 

 From Perm, Siberia, with emerald. 



Leucophane. Resembles somewhat a light green apatite. H=3 5. 

 Gr=2-97. Powder phosphorescent. Pyro-electric. Composition, silica 

 47-8, glucina 115, lime 250, protoxyd of manganese 1*01, potassium 

 0*3, sodium 76, fluorine 6*2. From Norway in syenite, accompanying 

 albite and elaeohte. 



Helvin. Helvin occurs in Saxony and Norway in tetrahedrons of a 

 wax yellow or brownish color. H=6 — 6'5. Gr=31 — 33. Luster 

 vitreous. It contains silica, oxyds of iron and manganese, sulphuret of 

 manganese, with glucina and alumina. 



6. ZIRCONIA. 



ZIRCON. 



Dimetric. In square prisms and octahedrons. M : e = 

 ^V. 132° 10 ; e : e = 123° 19. Cleavage parallel to 

 ft *<?j^1 M, but not strongly marked. Usually in crystals ; 

 but also granular. 



Color brownish-red, brown, and red, of clear 



tints ; also yellow, gray and white. Streak un- 



colored. Luster more or less adamantine. Often 



transparent ; also nearly opaque. Fracture con- 



choidal, brilliant. H = 7-5. Gr=4«0— 4-8. 



How does chrysoberyl differ from beryl 1 Where and how does it 

 occur 1 What is the origin of the name chrysoberyl ? What are its 

 uses ? Describe zircon ? 



