GREEN SAND. 



GREEN SAND. 



of the stratum which consist largely of the 

 green sand. 



"The water, percolating through the overly' 

 ing sands, and also through the pervious green 

 sand itself, has effected, and is daily effecting, 

 important changes in the condition of the shells 

 and other fossils; sometimes replacing their 

 carbonate of lime with oxide of iron, sometimes 

 removing it altogether, and leaving a mere 

 m<mld, forming either an inner or an outer 

 cast, and sometimes obliterating nearly every 

 traco of their former presence. 



"The total thickness of the green sand for- 

 mation, estimating it from the bottom of the 

 lou-mnost layers abounding in the green gra- 

 nular mineral to the overlying yellow ferrugi- 

 nous sands, or the limestone bed, when this is 

 present, may be stated approximately at about 

 one hundred feet. The only place in the whole 

 district where it is practicable to ascertain, 

 with any approach to accuracy, either the depth 

 of the formation, or the relative situation and 

 number of the separate beds which it comprises, 

 is along the shore of Sandy Hook bay, in the 

 cliffs of the Nevesink highlands, this, the 

 only coast section of the strata, is still an im- 

 perfect one ; large masses of the upper beds, 

 fallen from above, covering the lower deposits 

 near the water-side. 



"Owing to the large amount of water which 

 it usually contains, the green sand is rarely 

 penetrated in the numerous diggings which are 

 made in it for the marl, to a greater depth than 

 about twenty feet, the pits becoming at that 

 limit too wet to be prosecuted deeper. 



"In one or two instances, wells have been 

 sunk through the stratum, and the depth of the 

 green sand "ascertained to be about thirty feet, 

 as already mentioned. 



"Specific Gravity. The specific gravity of the 

 green granular mineral, carefully freed from 

 all extraneous adhering matter, is, according 

 to several experiments cautiously made, about 

 2-65. Three different specimens, taken from 

 remote localities, gave for the two lowest each 

 2-63 ; for the highest, 2-70. 



"The hardness of this mineral varies mate- 

 rially, being dependent somewhat upon the 

 time elapsed after it has been dug: it is softest 

 when moist and recently uncovered. Freshly 

 extracted, its hardness often does not exceed 

 that of talc; but when long uncovered and dry, 

 it nearly equals that of gypsum. 



"It would appear by experiment to be en- 

 tirely insoluble in water, both cold and boiling; 

 but it dissolves with tolerable facility in any 

 of the stronger acids, though different speci- 

 mens vary materially in this respect." 



The experience of farmers, continued through 

 nearlv half a century, had amply tested the 

 utKity of green sand as an active fertilizer 

 whf.n spread upon the ground. Various were 

 me views maintained in regard to its active 

 principles, and much speculation was, as usual, i 

 indulged upon the subject. The demonstra- ! 

 tion, made first by Mr. Henry Seybert, of Phi- 

 ladelphia, that the green sand of New Jersey 

 contained a considerable amount of potash, 

 seemed tc afford a very satisfactory clue by 

 which its mysterious effects might be traced 

 Mil 



588 



Chemical composition of Green Sand. From a 

 number of analysis of specimens of this mine- 

 ral, selected with the greatest care by Professor 

 Rogers, and ascertained to be entirely free 

 from extraneous matter, it would seem that it 

 is not quite uniform in its composition, but ex- 

 hibits slight variations in the proportions of 

 its principal constituents. The following re- 

 sults will serve to display the prevailing 

 chemical nature of green sand, and the mode- 

 rate variation of the several ingredients: 



Green Sand of Squankum. 

 Description. Colour, a dark olive-green ; 

 granules of a medium size ; it composes 58-36 

 per cent, of the marl of the upper part of the 

 bed, and 72-36 per cent, of the lower. 

 Composition. In 100 parts : 



Silica 51-00 



Alumina ----- 6-50 



Protoxide of iron - 2J-55 



Potash ----- 10-50 



Lime ------ a trace. 



Magnesia - - - - - 1-08 



Water 9.00 



99.63 



Greensand of Freehold, Monmouth County. 

 Description. Colour of the granules, rich 

 green ; size, small ; composes 70 per cent, of 

 the upper part of the bed, and 50 per cent, of 

 the lower. 



Composition. In 100 parts : 



Silica 50-00 



Alumina ----- 7-00 



Protoxide of iron - - - 22 00 



Potash 11-00 



Lime 1-00 



Magnesia - - - - - a trace. 



Water 9-00 



100-00 

 Green Sand of the Marl of Poke Hill, near Plaits- 



burg, Burlington County. 

 Description. Colour of the granules, a rich 

 dark olive-green; their size, rather above the 

 medium ; composes 98 per cent, of the marl. 

 Composition. In 100 parts: 



Silica 50-75 



Alumina ----- 6-50 

 Protoxide of iron - 22-14 



Potash ----- 12-96 

 Water 7-50 



9985 



Comparing the details of the several analy- 

 ses furnished by Professor Rogers, we perceive 



hat the green sand, even when of the greatest 



mrity, is not absolutely constant, either in the 

 nature of the ingredients which enter into its 

 composition, or in their relative proportions. 

 The per centage of the silica varies from 47-5 



o 51-5; that of the alumina from 6 to 9-35; 



hat of the protoxide of iron from 20-86 to 

 24-74; that of the potash from 9-96 to 12-96; 

 and that of the water from 5-5 to 9-5. We 

 find, moreover, that, in some instances, be- 

 sides these elements, lime enters into the con- 

 stitution of the green sand, in other cases mag- 

 nesia; while, occasionally, both occur. The 

 amount of these earths is, however, always in- 

 considerable. 



It appears that the mean proportion of the 

 silica is approximately 49-5 per cent. ; that of 

 the alumina 7-3; of the protoxide of iron 22-8; 

 of the potash 11-5; and of the water 7-9 per 



