On the mineralogy of the counties of Dublin and Wicklow / by Samuel Haughton.

  • Samuel Haughton
Date:
[1878]
Catalogue details

Licence: Public Domain Mark

Credit: On the mineralogy of the counties of Dublin and Wicklow / by Samuel Haughton. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the following simultaneous equations, to determine the per-cent- ages of the constituent minerals in the average granite :— Let Q = the per-centage of Quartz. O )) Orthoclase. A )) )) Albite. W White Mica. B Black Mica. (1) Silica, 7207 =100 Q+ 64-95 0 + 64-70 A + 44-58 W + 35-55 B. (2) Alumina, 1481 = — 18-31 0 + 21-80 A+32-13 W + 17-08 B. (3) Iron peroxide, . 225 = — _ _ 4-57 W + 23-7 B. (4) Lime, 163 = — 0-25 0 — 0-78 W + 0-61 B. (5) Magnesia, 33 = — 0-58 0 — 0-76 W + 3 07 B. (6) Potash, . 511 = — 12-23 0+ 2-84 A + 10-67 W+ 9-45 B. (7) Soda, 279 = — 2-75 0+ 9-87 A + 0-95 W + 0-35 B. (8) Loss by ignition, 109 = — _ _ 5-34 W + 4-30 B. Jf we select the four equations containing the largest per-cent- ages, viz—The alumina, potash, soda, and iron peroxide equations, we find after several reductions— A = 18-0 + 0-156 W -f- 0-191 B. O = 37-65 — 0-909 W — 0-819 B. These equations show the manner in which the two feldspars are related to the two micas. We find finally— B = 5-81 percent. W= 19-16 O = 15-44 A = 22-10 Inserting these values into the last seven equations, we ob- tain— Observed. Calculated. Diff. Alumina, 1481 1476-06 + 4-94 Iron peroxide, . 225 224-99 + 0-01 Lime, .... 163 22-28 + 140-72 Magnesia, 33 41-27 -8-27 Potash, .... 511 511-45 -0-45 Soda, .... 279 28064 — 1-64 Loss by ignition, 109 126-89 -17-89 The agreement between calculation and observation is as close as could be expected ; and the errors in the magnesia and loss by ignition, are, doubtless, errors of observation, due to the small magnitudes to be ascertained. The excess in the lime is real, and must be accounted for by the existence of a small quantity of paste, in the form of a silicate of lime.
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