Subsurface and Office Representation in Mining Geology 1033 



tion trend. A line is sufficient to indicate the described point; it should 

 be straight, not curved, with no unnecessary "jogs," or direction barbs. 



On note sheets, textural and compositional gradations are indicated 

 at gradational-interval-end points by side-note descriptions joined with a 

 line. 



Compositional or textural gradation ("fading") is also indicated as 

 shown in the lower central portion of figure 543. Abbreviations and chem- 

 ical formulae are utilized when possible. The abbreviations should be 

 "natural" and non-ambiguous; e.g. chalcocite, CuaS; pyrite, FeS2; bornite, 

 Born; covellite, CuS; quartz, Qtz; silicate or siliceous, Sil; augite, Aug; 

 hornblende, Hb; feldspar, Feld; gouge, Gg; fault, Fit. Non-complex 

 minerals are always designated by chemical formulae (pyrrhotite, Fen- 

 S12) ; silicates by first syllable (garnet, Gar) ; and other terms by omitting 

 vowels (jointed, Jtd). Successive nouns are separated by commas; succes- 

 sive adjectives are not punctuated. Only descriptive material is included 

 in side notes; e.g., "sooty" chalcocite is preferably over "secondary" 

 chalcocite. Descriptions should indicate observations rather than deduc- 

 tions. Properly recorded observations facilitate deduction at any later 

 date. Side notes are so recorded that a maximum of space is available 

 for detail, and precise comprehension by persons other than geologists is 

 possible. 



Note Sheet Dating and Signing — The mapping date and geologist's 

 initials are indicated on the reverse side of the sheet in the mapped-area 

 space. The mapped-area position is determined by holding the sheet 

 to the light. 



Sectional Specifications — Cultural and engineering data posting is 

 the ?ame on plan and section. Wlienever possible, sectional representation 

 is on either north-south or east-west vertical plane orientation, as indicated 

 in figure 544. Apparent dip corrections are made, therefore, before angu- 

 lar data is posted. 



Cross-section data are readily integrated for ore finding if the section 

 plane coincides with the even hundred ordinate lines. Nothing is gained 

 by preparing sections at right angle to the vein strike; a section will prob- 

 ably be at an acute angle to cross-cutting faults also represented on the 

 section. 



The degree of cultural- or geologic-data probability and reliability 

 are indicated thus: 



1. Known Data: 



a. Known location. 



Data, located on the sectional plane, are posted as on maps. 

 Projected data to the sectional plane are represented by long 

 dashes. Spacing distance indicates projection distance. Dis- 

 tance and direction of projection are indicated thus: "25' 

 E." 



