HOBBS — MINERALOGY OF WISCONSIN. 137 



BARITE FROM THE LINDEN MINE. 



Barite or barytes, as it is called at the mines, has been 

 found massive in considerable abundance at a number of 

 localities in the eastern portion of the mining region. 

 Specimens from Mineral Point, Crow Branch Mine, the 

 Welsh Settlement in Iowa county, and the Linden Mine, 

 are included in the University Collection. The mineral is 

 almost invariably crystalline, as is shown by its cleavage 

 and by the projection of indeterminable crystal edges from 

 its knobby surfaces. Crystals have been reported from 

 Scale's Mound just over the interstate boundary in Illinois. 

 I have not been able to examine any specimens from this 

 locality. A few crystals of the mineral were, however, 

 found attached to one of the faces of the larger twinned 

 crystal of calcite from the Linden Mine, which has already 

 been referred to in this paper. These crystals of barite are 

 represented in plate 7, figure 4. They have a maximum 

 length of about a centimeter and a half, are of a light gray 

 or brown color, and possess a rather unusual habit. They 

 are lath-shaped, approaching acicular, with the direction of 

 principal development the macro-diagonal axis. This fact 

 is easily determined, since the acute angle of the perfect 

 prismatic cleavage is found at the extremities of the crys- 

 tals. The narrow tabular plane which forms the top of 

 the laths is the basal pinacoid, since it is parallel to the best 

 cleavage. The other planes present are m, ooP (110) and 

 d, ^Poo (102). The former can be seen to be parallel to 

 the second cleavage, and the latter has been determined 

 with sufficient accuracy by the following measurement 

 made upon the reflecting goniometer, the face c affording 

 a fair and d a much blurred image of the signal: 



Measured. Calculated, 



c : d, 001 : 101 37° 45' 38° 51'. 



Most of the faces are dull and reflect poorly, but poor 

 as the measurements are they are the best that were pos- 



