RAW QUARTZ, ITS DEFECTS AND INSPECTION 343 



other substances that might have been present during growth conditions. 

 That these cavities are seldom in the form of negative crystals, i.e. having the 

 plane natural faces characteristic of quartz, is not easily explained. 



NEEDLE INCLUSIONS appear as long, thin lines or needles. They 

 may be straight or curved, blue, white or otherwise. Whether they are 

 continuous or composed of rows of individual inclusions is usually not dis- 

 cernable. Needles, visible without concentrated illumination (and fluid 

 immersion), are likely to be inclusions of crystalline material, such as rutile 

 (brown), tourmaline (black). Usually such needles are called rutile needles, 

 because of the commonness of rutile and the difficulty of determining whether 

 they are rutile or some other material. They might better be called DARK 

 needles. BLUE NEEDLES are fine textured, and may appear singly or in 

 parallel groups, which may be at angles to other parallel groups. In other 

 cases they spread from a bubble point, like a comet. Blue needles may also 

 be feathered (having short feathery rays along the sides), may be hard (very 

 fine and sharply distinguishable), or soft (diffuse). Probably the most 

 important characterization of all blue needles is their blueness, which in- 

 dicates fine texture. WHITE NEEDLES are similarly hard or soft. 

 CHUVA is a special type of white needle which would be extremely elusive 

 except for the fact that along its length are small bubbles, giving chuva the 

 appearance of dew drops along a thin fiber. For piezoelectric usage an 

 important distinction between needles is whether they are blue, white, chuva, 

 or dark. 



PHANTOMS are an arrangement form of inclusions (or coloration), in 

 plane sheets which are parallel to possible natural crystal faces (usually the 

 prism or pyramid faces). Often several, differently oriented, phantom 

 planes are formed together so as to give the appearance of a crystal within a 

 crystal, thus the name phantom (or ghost). Phantoms may also appear as 

 groups of parallel sheets. Phantoms may be of smoky, blue, white, or 

 bubble texture and should be so noted when describing their effects on 

 piezoelectric elements. That phantoms are closely related to disturbed 

 growth conditions is apparent from their close relationship to crystal faces. 



VEILS are an arrangement form of inclusions in curved sheets. They 

 are most commonly of a tenuous bubble texture, but may also be white or 

 bluish. Again this distinction is of importance in estimating their deleteri- 

 ous effects. The cause of inclusions appearing in veil form is not clear. 



CLOUDS (a term not widely used) refer to inclusions irregularly dis- 

 tributed in restricted regions of the crystal. 



4.7 Inspection Means 



The raw quartz inspectoscope is the name of an instrument used for the 

 inspection of raw^ quartz. This inspectoscope may, of course, be also used 



