SALMON — RESEARCHES ON PSEUDOMORPHS. 



397 



wMck compose the terrestrial crust contain but a small number of 

 minerals.* It seems even that certain minerals were unable to form 

 themselves without others being developed at the same time. Thus, 

 when there are felspars in a rock, we also most usually find the 

 micas, augite, or hornblende. Similarly it is rare for orthoclase to 

 be met with, without quartz. The associations of minerals are be- 

 sides observed as well in normal and in abnormal rocks. In addition, 

 as has been shown by Messrs. Breithaupt, Henwood, and B. Cotta, 

 the minerals have generally succeeded in the same order.f It can- 

 not, therefore, be doubted that minerals manifest a great tendency to 

 form constant associations. 



There is eminently one particular case in which the associations 

 are very evident, and as intimate as possible ; it is when two minerals 

 are crystallized in such a manner that the one envelopes the other : 

 we then say that there is envelopment. 



Envelopment. 



The envelopment of minerals is well fitted to throw light on the 

 conditions in which they were formed, and has consequently attracted 

 special attention. The older geologists occupied themselves with 

 this subject, particularly Rome de I'lsle, De Bournon, Haiiy, Ger- 

 hard, Grallois, Grermar, Marx, Yon Born, Werner, Karsten, Mohs, 

 Chrichton, and Phillips. More recently, it has been noticed in 

 diverse circumstances by Messrs. Breithaupt, ^aumann, Gr. Bischof, 

 Haussmann, Haidinger, Scheerer, G. Hose, Sillem, Zippe, Von 

 Zepharovitch, Tamnau, Wieser, Wiebye, A. Knop, Websky, Mar- 

 bach, Genth, Liebener, Null, Levy, Durocher, Sir David Brewster, 

 H. 0. Sorby, Silliman, Alger, Mcol, Jackson. But it is particularly 

 to Messrs. R. Blum, G. Leonhard, Kenngott, A. SeyfFert, and 

 Sochting, that we owe the principal labours on envelopment. J 



When we regard the question in its widest generality, one mineral 

 may envelope an almost indefinite number of other minerals ; the old 

 popular maxim, " tout est dans tout," seems to be verified for the 

 mineral kingdom. 



However, the number of minerals enveloping and enveloped is not 

 so gTeat as we might at first sight suppose ; indeed, they may be 

 considerably reduced if we limit them to those which are well crys- 

 tallized, and the most important. 



The following is a table which gives a resume of these, and shows 

 us the envelopment of the principal minerals. The classification 

 adopted is that of Mr. Dana (" System of Mineralogy"). The en- 

 veloping mineral is given in the first column of the talDle, and the 



* On tMs subject see my paper " On Eocks." " Geologist," vol. ii., p.p. 49 

 and 22.— H. C. S, 



t Breithaupt, " Paragenesis der Mineralien." Henwood, " Phil. Mag. :" 1846, 

 p. 360. B. Cotta, " Erzlagerstatten 2nd ed., p. 72. 



X " Naturw. Verein in Halle," 1853, t. xi, : 6, Hollandische Societat der Wis- 

 senschaften zu Haarlem : 1854. 



