Show q SERIES OF ANALYSES OF MINERALS ISSUED To the so called caled practical ml mind d' d an an n analysis of a rock or mineral is useful only because it i may show the tile Intrinsic value In dollars dolar and cents of the rock or mineral analyzed but In a larger view a miner series of such analyses like those just published by the geological survey sureY as its bulletin 41 has more than a merely commercial 4 value The determination of rode rock and mineral species Is of prime Importance Im im- im- im to the tho geologist in his his' work and the aid of the chemist Is frequently required In that determination To understand understand understand un un- un- un the how and the why why of things as they are Is no less essential In than In other branches of petrography science and In this search the man Inthe in inthe inthe the laboratory c operates cO-operates wi with h the man manBy manIn manin In the field feld S By means of ot chemical analyses an en- en entirely en en- new hew system of rock classification has been devised This system is applicable applicable ap ap- ap- ap to all al Igneous rocks and Is comIng coming cornIng com corn ing Into rather general generl use among pe- pe for it is more exact and ande m more sl significant than i n any older system The e bulletin ft just j published p rIS c contains tt 1750 analyses of ot rocks and soils sois of or minerals and 62 of meteorites It I was compiled by F. F W. W Clarke Clarl e. e chief chemist aVId and work represents done in t the an chemical important In laboratory a part t of t the of the survey Ece between between 1880 1850 and anti 1908 These surveY are available to show the chemical and mineral composition of the earths earth's crust the crust the the only part of the earth earh's of which we have hare any knowledge More than half of it consists of oxygen ogen with other other-cle other cle clements held In combination wih many man othele othe le ments Silica Sica an oxide of the element silicon forms about 61 per cent is the preponderant constituent In all al rocks except the an all oxide of aluminum constitutes about 15 per cent Iron in combination with the ever present oxygen makes up about 6 per tier cent cent Magnesium calcium sodium and potassium occur in smaller proportions lions ranking in the order named tons The bulletin Is In part a a reprint of several others that are now out of print and will be of wide general uso use to chemists wi and It I can be bo obtained without charge by applying to the director of or the survey surrey at Washington ashington |