large Crystals of Enstatite. 381 



38 centims. in length, 26 in breadth, 13 in thickness ; the 

 other one, notwithstanding its being broken at both ends, is 

 still 40 centims. long. 



The crystals show a predominating vertical rhombic prism, 

 whose edges are nearly rectangular. The makropinakoid is 

 much developed, whilst the brachypinakoid is only small. An 

 evident rhombic symmetry is seldom to be recognized on the 

 summits of the crystals ; it offers, on the contrary, a pseudo- 

 monoclinic appearance. A very characteristic feature of the 

 crystals is the great number of often, repeated faces, and with 

 small inclinations which form a shallow vaulted summit. We 

 shall return to the study of the crystalline form after a brief 

 sketch of the physical and chemical properties. The surface 

 of the crystals offers a steatitic appearance ; the faces are dull. 

 This steatitic crust is only thin, reaching at the utmost 10 

 millims. into the interior. There are two perfect cleavages, 

 parallel to the prismatic faces ; the third, parallel to the bra- 

 chypinakoid, is imperfect. The lustre of the first two is pearly, 

 whilst that of the imperfect cleavage is only glistening. Nu- 

 merous undulated fissures seen on the cleavage-faces are con- 

 nected with the metamorphosis into steatite. It is very inter- 

 esting by means of the microscope to observe the gradual 

 change of enstatite into the hydrous combination. The specific 

 gravity of our enstatite is 3*153. The composition is as fol- 

 lows: — 



Si0 2 = 58-00 = 30-93 

 A1 2 3 = 1-35 „ 0-63 



FeO = 3-16 „ 0-70 



MgO =36-91 „ 14-76 



H 2 = 0-80 



100-22 



These numbers resemble closely the composition of the Mo- 

 ravian specimen from the Zdjar Mountain, and those of the 



cosmical en 



statites from Bishopville an 



d Busti, 









We also 



analyzed the steatitic crust, 



whose 



specific 



gro 



rity 



= 2-867. 



Si0 2 



A1 2 3 



FeO 



CaO 



MgO 



H 2 



= 57-62 

 = 1-48 

 = 1-96 

 = 0-12 

 = 34-72 

 = 4-38 











100-28 

 So that the only change is the introduction of water. 



