﻿306 
  W. 
  Lino 
  1 
  gr 
  en 
  — 
  Granitic 
  Rocks 
  of 
  California. 
  

  

  than 
  the 
  granodiorite, 
  and 
  its 
  areas 
  include 
  the 
  highest 
  and 
  

   roughest 
  ridges 
  in 
  the 
  region. 
  For 
  the 
  same 
  reason 
  bowlders 
  

   and 
  cobbles 
  of 
  granitite 
  are 
  much 
  more 
  abundant 
  than 
  those 
  of 
  

   granodiorite. 
  While 
  it 
  varies 
  somewhat 
  in 
  appearance 
  and 
  

   constitution, 
  yet 
  it 
  is 
  a 
  typical 
  granite. 
  The 
  rock 
  is 
  coarse- 
  

   grained 
  and 
  has 
  often 
  a 
  decided 
  tendency 
  towards 
  a 
  rough 
  

   porphyritic 
  structure. 
  The 
  orthoclase 
  appears 
  as 
  large 
  grains 
  

   and 
  imperfect 
  prisms 
  of 
  reddish 
  gray 
  color 
  up 
  to 
  two 
  or 
  even 
  

   three 
  centimeters 
  long 
  ; 
  the 
  quartz 
  is 
  very 
  prominent 
  in 
  dark- 
  

   gray 
  rounded 
  grains 
  up 
  to 
  one 
  centimeter 
  in 
  diameter, 
  while 
  

   the 
  black 
  mica 
  and 
  smaller 
  quartz 
  and 
  feldspar 
  grains 
  lie 
  

   between 
  these 
  larger 
  constituents. 
  Hornblende 
  occurs 
  only 
  

   rarely 
  ; 
  when 
  it 
  appears 
  plagioclase 
  usually 
  also 
  enters 
  into 
  

   the 
  composition, 
  and 
  transition 
  -forms 
  to 
  granodiorite 
  result. 
  

  

  Table 
  of 
  Analyses 
  of 
  Granitic 
  Rocks. 
  

   Analyst: 
  Mr. 
  Geo. 
  Steiger. 
  

  

  I 
  II 
  III 
  IV 
  V 
  YI 
  YII 
  YIII 
  IX 
  

  

  Si0 
  2 
  --- 
  77-68 
  72-95 
  67'45 
  68-13 
  67-14 
  68-32 
  65 
  88 
  51-47 
  57-11 
  

  

  Ti0 
  2 
  -14 
  -58 
  

  

  A1 
  2 
  3 
  11-81 
  15-51 
  

  

  Fe 
  2 
  3 
  -72 
  1-76 
  

  

  FeO 
  -51 
  221 
  

  

  MnO 
  trace 
  

  

  CaO 
  -72 
  1-16 
  360 
  3-51 
  4-07 
  3-21 
  4-11 
  1018 
  5-32 
  

  

  MgO 
  -18 
  1-10 
  

  

  K 
  2 
  500 
  5-43 
  3-66 
  3-58 
  2 
  70 
  3-37 
  2"88 
  T08 
  411 
  

  

  Na 
  2 
  2-96 
  374 
  3'47 
  3*13 
  3'09 
  2'51 
  2"41 
  2'86 
  3'06 
  

  

  Water 
  100- 
  04 
  -14 
  

  

  Water 
  100+ 
  '21 
  -63 
  

  

  P 
  2 
  6 
  -10 
  -12 
  

  

  100-13 
  100-25 
  

  

  I. 
  164 
  Pyramid 
  Peak 
  collection; 
  granitite: 
  Placerville 
  Ditch 
  r 
  

   J 
  mile 
  north 
  of 
  Ditch-camp 
  7. 
  Lat. 
  38° 
  45 
  5' 
  ; 
  Long. 
  

   120° 
  36-1'. 
  

   II. 
  20 
  Pyramid 
  Peak 
  collection 
  ; 
  granitite; 
  south 
  side 
  Pyra- 
  

   mid 
  Peak, 
  1,200 
  feet 
  below 
  summit. 
  Lat. 
  38° 
  

   50-2'; 
  Long. 
  120° 
  9-5'. 
  

  

  III. 
  103 
  Pyramid 
  Peak 
  collection 
  ; 
  granodiorite; 
  road, 
  £ 
  mile 
  

  

  west 
  of 
  Silver 
  Lake 
  House. 
  Lat. 
  38° 
  39-8'; 
  Long. 
  

   120° 
  7-1'. 
  

  

  IV. 
  69 
  Pyramid 
  Peak 
  collection; 
  granodiorite; 
  trail 
  Emer- 
  

  

  ald 
  Bay 
  to 
  Rubicon 
  Point, 
  1^ 
  mile 
  south 
  of 
  latter. 
  

   Lat. 
  38° 
  48-6'; 
  Long. 
  120° 
  6*3'. 
  

   V. 
  86 
  Pyramid 
  Peak 
  collection: 
  granodiorite; 
  1 
  mile 
  E.S.E. 
  

   of 
  Rockbound 
  Lake. 
  Lat. 
  38° 
  58*8'; 
  Long. 
  120° 
  

  

  13-r. 
  

  

  VI. 
  120 
  Pyramid 
  Peak 
  collection 
  ; 
  granodiorite 
  ; 
  Big 
  Mud 
  

   Lake 
  bears 
  N. 
  30° 
  W. 
  and 
  is 
  l£ 
  mile 
  distant. 
  Lat. 
  

   38° 
  35-6'; 
  Long. 
  120° 
  9'. 
  

  

  