CATALOGUE OF GEMS AND PRECIOUS STONES. 49 



North Carolina. 

 Rutherford County: 



Uncut; pale yellow; 0.14 carat; 3 mm. diameter; flattened octahedron. 

 The Shepard collection No. 1002 



Diopside. — See under P}roxene. 

 Emerald. — See under Beryl. 



EPIDOTE. 



Composition. — Calcium aluminum iron orthosilicate, Ca 2 (Al,Fe) 3 

 (OH)(Si0 4 ) 3 . 



Crystallization. — Monoclinic. 



Color. — Brown, green, green-yellow, or green-brown, owing to the 

 presence of iron; strongly pleochroic, green to brown. 



Luster. — -Vitreous. 



Hardness. — 6.5 ; fairly durable. 



Specific gravity. — 3. 30 ±0.10. 



Optical properties. — Mean refractive index 1.75; double refraction 

 strong, 0.04; optically biaxial, negative. 



With the microspectroscope epidote shows an absorption band in 

 the violet. The color of the mineral is its most distinctive quality. 

 It occurs in met amorphic rocks and in veins, and is little used as a 

 precious stone owing to its intense color. 



LIST OF SPECIMENS. 



TYROL. 



Step, rectangular girdle; dark hrown; 3.92 carats; 14 by 8 by 3 mm No. 579 



Step, rectangular girdle; dark green; 0.74 carat; 8 by 4.5 by 2 mm No. 580 



Essonite. — See under Garnet. 



EUCLASE. 



Composition. — Beryllium aluminum orthosilicate, BeAl(OH) (Si0 4 ). 



Crystallization. — Monoclinic. 



Color. — Colorless when pure, but often colored pale green or blue 

 by traces of iron. 



Luster. — Vitreous . 



Hardness. — 7.5; very durable. 



Specific gravity. — 3.10 ±0.05. 



Optical properties. — Mean refractive index 1.66; double refraction 

 moderate, 0.02; optically biaxial, positive. 



The mineral can be distinguished only by its optical properties. 

 Occurs in met amorphic locks such as mica schist, but it is rare and 

 not widely used as a gem. 



LIST OF SPECIMENS. 

 BRAZIL. 



Step-brilliant, square girdle; pale green; 1.06 carats; 7 by 4 mm No. S32 



Fairy Stone. — See under Staurolite. 



