GEE 



[ 205 ] 



GEE 



always appears in the form of 

 earthy particles of a deep green 

 tint. The green matter, when not 

 previously weathered, is very feebly 

 attacked by concentrated acids. It 

 gives out water when heated, and 

 becomes brown from its iron passing 

 into the state of peroxide. As it 

 has been supposed to owe its green 

 colour to the presence of phosphoric 

 acid, it was carefully examined, 

 with the view of detecting that 

 acid, if present. The result proved 

 that lime and phosphoric acid are 

 not essential constituents of the 

 colouring matter of green- sand, and 

 their presence must be regarded as 

 casual. The green particles have 

 been found to consist of silica 48*5, 

 black oxide of iron 22, alumina 17, 

 magnesia 3 f 8, water 7, and potash 

 some traces : M. Berthier gives of 

 potash 10, as found in some green 

 particles from near Havre." In 

 describing the group of deposits 

 to which the name of green- sand, 

 or Shanklin-sand, is appropriated, 

 geologists state that they admit of 

 a triple division ; the first, or 

 uppermost, consists of sand, with 

 irregular concretions of limestone 

 and chert, sometimes disposed in 

 courses oblique to the general di- 

 rection of the strata. The second 

 consists chiefly of sand, but in some 

 places is so mixed with clay, or 

 with oxide of iron, as to retain 

 water. The third, and lowest 

 group, abounds much more in 

 stone ; the concretional beds being 

 closer together and more nearly 

 continuous. The total thickness of 

 the green-sand, where it is fully 

 developed, is more than 400 feet. 

 The animal remains of the green- 

 sand are exclusively marine. The 

 fossils principally hitherto dis- 

 covered in the green-sand group 

 are, Inoceramus, Cuculla3a, Pecten, 

 Vermetus, Solarium, Mya, Nucula, 

 Natica, Nautilus, Dentalium, Bel- 

 emnites, Ammonites, Hamites, 



Thetis, Siphonia, Corbula, Sphgera, 

 Trigonia, Diceras, Modiola, Avicula, 

 Gervillia, Terebratula, Limo, Lito- 

 rina, Eostellaria, Pusus, &c. The 

 French have denominated this for- 

 mation glauconie crayeuse, and 

 craie chloritee. It is very common 

 to divide the greensand into the 

 upper green-sand and the lower 

 green-sand, the two being separated 

 by the gault. 



GREE'NSTONE. The Griinstein of 

 Werner; Eoche Amphibolique of 

 Haiiy ; the diabase of the Prench 

 geologists. A granular rock com- 

 posed of hornblende and felspar, in 

 the state of grains, or sometimes of 

 small crystals. Greenstone contains 

 a larger quantity of felspar than 

 basalt, and the grains both of 

 hornblende and felspar are less 

 amalgamated. It is a variety of 

 trap rock. The hornblende usually 

 predominates, and frequently gives 

 to this aggregate a greenish hue, 

 from which circumstance it obtains 

 its name. Greenstone occurs in 

 beds of considerable magnitude, 

 and sometimes forms whole moun- 

 tains. It often appears in conical 

 hills, or presents high, mural 

 precipices, whose fronts are fre- 

 quently composed of numerous 

 columns of various sizes, resemb- 

 ling basalt. Sometimes it forms 

 only the summits of moun- 

 tains. Small veins of actinolite, 

 epidote, felspar, prehnite, quartz, 

 &c., &c., frequently are found 

 traversing greenstone. "When 

 greenstone is decomposed it pro- 

 duces a reddish brown soil. The 

 presence of green-stone, even when 

 concealed from view, is oftentimes 

 declared by the reddish brown 

 colour of the soil, the tint varying 

 in depth according to the propor- 

 tion of the hornblende in the rock. 



GEEIES-STONE. A rock composed of 

 quartz and mica in a peculiar state 

 of aggregation. Greiss-stone occurs 

 in Cornwall. 



