DIAPHANEITY — LUSTRE COLOR. 71 



Example, fibrous calcite, fibrous gypsum, and many fibrous 

 minerals, more especially those which in other forms have a 

 pearly lustre. 



6. Adamantine — the lustre of the diamond. When sub- 

 metallic, it is termed metallic adamantine. Example, some 

 varieties of white lead ore or cerussite. 



b. The degrees of intensity are denominated as follows: 



1. Splendent — when the surface reflects light with great bril- 

 liancy and gives well-defined images. Example, Elba hematite, 

 tin ore, some specimens of quartz and pyrite. 



2. Shining — when an image is produced, but not a well-de- 

 fined image. Example, calcite, celestite. 



3. Glistening — when there is a general reflection from the 

 surface, but no image. Example, talc. 



4. Glimmering — when the reflection is very imperfect, and 

 apparently from points scattered over the surface. Example, 

 flint, chalcedony. 



A mineral is said to be dull when there is a total absence of 

 lustre. Example, chalk. 



3. Color. 



1. Kinds of Color. — In distinguishing minerals, both the ex 

 ternal color and the color of a surface that has been rubbed oi 

 scratched, are observed. The latter is called the streak, and the 

 powder abraded, the streak-powder. 



The colors are either metallic or unmetallic. 



The metallic are named after some familiar metal, as copper- 

 red, bronze-ycilow, brass-yellow, gold-yellow, steel-gray, lead- 

 gray, iron-gray. ^ 



The unmetallic colors used in characterizing minerals are 

 various shades of white, gray, black, blue, green, yellow, red, and 

 brown. 



There are thus snow-white, reddish-white, greenish-white, 

 milk-white, yellowish- white. 



Bluish-gray, smoke-gray, greenish-gray, pearl-gray, ash-gray. 



Yelvet-black, greenish-black, bluish-black, grayish-black. 



Azure-blue, violet-blue, sky-blue, indigo-blue. 



Emsrald-green, olive-green, oil-green, grass-green, apple-green, 

 bUckish- green, pistachio-green (yellowish). 



Sulphur-yellow, straw-yellow, wax-yellow, ochre-yellow, 

 honey-yellow, orange-yellow. 



Scarlet-red, blood-red, flesh red, brick-red, hyacinth-red, rose- 

 red, cherry-red. 



