TRAVELS IN BRAZIL. 



and bevilled at the other, by planes obliquely set on the 

 acute lateral edges, so that the edges of bevilment form 

 with the obtuse lateral edge an angle of 133°, and the 

 bevilled planes meet under one of 106°. At the upper 

 corner of the bevilment, there are four other small planes, 

 which make a kind of acumination ; two of these planes 

 are smooth, the two others clearly notched, and show, as in 

 the topazes, that the crystal is composed of several small 

 ones. The lateral planes are longitudinally striated, and 

 curved towards the obtuse lateral edge, so that the crystal 

 has a reed-shaped appearance. The striation of the lateral 

 planes most probably arose from the accumulation of the 

 abovementioned smaller crystals, which formed several little 

 planes, that are divided by furrows, whence the angles of 

 the lateral edges can only be measured at the sharp edge. 



In the pieces of euklase in our possession, we observed only 

 one cleavage, namely, in the direction of the short diagonal 

 of the terminal planes, or across the acute lateral edges, 

 and which is in the highest degree perfect. The transverse 

 fracture appears conchoidal. Some lateral and terminal 

 planes of the crystals are rough, with numerous small im- 

 pressions caused by the scales of the lithomarge, as in the 

 emerald and topaz, and thus leave no room to doubt that 

 this latter is their matrix. 



We have observed above, that with the topazes and 

 euklases, there occur also quartz and rock-crystals of dif- 

 ferent sizes; we will here particularise only two of the 

 former and two of the latter, which are deposited in the 

 Brazilian museum at Munich. 



A piece of greyish white transparent quartz, has no 

 regular shape, but the whole surface is full of impressions, 

 which are frequently deep, occasioned by topaz crystals. 

 Two fragments of the latter, of a light and dark yellow 

 colour, still grow together with it. 



The second piece of quartz is a six-sided prism, acumin- 

 ated at both ends with six planes, crystallised, large, pellucid, 



