OPTICAL MINEKALOGY 



tice mineral identification is expedited by merits such as Chayes point counter or Rosi- 



systematic etch tests with corrosive reagents wal stage. 



and by microchemical and x-ray analysis of (7) Index liquids for immersion studies. 



powder scratched from the surface of the A complete set includes liquids in the index 



polished section. range 1.40 to 2.0, approximately. To stand- 



For simple determination of minerals by ardize liquids an Abbe-type refractometer 



optical techniques apparatus requirements with temperature control suffices for the in- 



are not great, but for investigations of new dex range 1.40-1.80. Higher index liquids are 



minerals or for the purpose of establishing standardized in a hollow prism mounted on a 



accurate correlation of optical properties spectrometer. 



with composition, crystal structure, and (8) Equipment for sample preparation and 

 genetic history, extensive facilities are re- physical analysis. Included should be all ap- 

 quired. A well-equipped laboratory for the paratus necessary for cutting, grinding, and 

 examination of minerals by the methods of polishing thin sections and polished sections 

 mineralogy, including optical mineralogy, and placing in appropriate mounts for micro- 

 should include the following: scopic examination by transmitted or re- 



(1) Polarizing microscope with rotatable fleeted light. Crushing equipment and screens 

 stage, attachable 4-axis and 5-axis universal or elutriation equipment for particle-size sep- 

 stages, and attachable vertical illuminator aration or analysis are useful. 



for examining pohshed surfaces of opaque (9) Equipment and reagents formicrochem- 



substances. Appropriate optical accessories ical analysis, particularly for use with pol- 



and lenses. ished sections of opaque substances. 



(2) Temperature control equipment. This (10) Miscellaneous laboratory equipment, 

 should include apparatus for varying tem- including reflecting goniometers for crys- 

 perature of stage and hemispheres of uni- tal-angle measurement. Stereographic and 

 versal stage and a heating stage that can be equal-area nets for plotting crystallographic 

 attached to the microscope stage. A high- data, including optical data, 

 temperature furnace may be useful for (11) For correlation of optical data with 

 studies of certain thermal effects. chemical composition and crystal structure 



(3) Light sources. Included should be a facilities should be available for quantitative 

 white light source, a monochromator, and a chemical analysis, spectrographic analysis, 

 series of color filters. Also useful are a so- and x-ray study of single crystals and pow- 

 dium-vapor lamp, mercury-arc lamp, and a ^ers. Occasionally useful are differential 

 hvdroo-en-discharo-e tube thermal equipment, an electron microscope, 



(4) Spectrophotometric eciuipment for ^^^^ ^^ electromagnetic or electrostatic sep- 

 analyzing colored light transmitted by '^'^*^', ^^' 'Reparation of mineral fractions. 



mi • ■ J. 1 111 1 (12) For correlation of optical properties 



microscope. Ihis equipment should be de- .,, , . , . • -.i 



, , , ., . r ^^■ With complex miueral SBries, comparisoii With 



signed also to permit measurement oi ellip- ^i • i • i • ^10^.1- 



,. ., „ . , _ , ,. , ^ synthesized minerals is useful. Synthesis 



ticity of transmitted or reflected light, meas- , • , ui <• 



'^ ' commonly requires apparatus capable 01 gen- 



urement or rotation of plane of vibration of ^^^^-^^^ ^igh pressures and temperatures and, 



reflected light, and measurment of reflectiv- ^t times, withstanding the effects of corrosive 



ity of opaque specimens. fluids 



(5) Photomicrographic apparatus suitable 



for photographing specimens by transmitted , ^ , 



^ , ,. , ■ Allen, R. D., "A New Equation Relating Index 



or reflected light. ^^ Refraction to Specific Gravity," Am. Min- 



(6) Counting or measuring stage attach- eralogist, 41, 245-257 (1956). 



472 



