<= Se 
Fes. 1900. CrYSTAL FORMS OF CALCITE—FARRINGTON. 234 
These came from the Blakie No. 2 mine. The crystals which may 
be designated as Type No. 2 are characterized by a deep amber 
yellow color ranging to colorless. They come from the Crystal 
Cave, Ino mine. These two mines are quite near one another, and 
are both located in Leadville Hollow, within the city limits of Joplin. 
FORMS OF LARGE CRYSTALS, 
Type !.—Crystals of this type are very simple in form. They 
are made up of the common scalenohedron v, +R3,* truncated by 
the flatter scalenohedron ¢, +4%R3. The average development of 
the forms is illustrated in Fig. 1, Pl. xxviii, it being drawn one-half 
size from one of the crystals in the Museum collection. Such a 
size is usual to crystals of this type. The following are averages 
of measurements of several angles on crystals of this type, as made 
with a contact goniometer: 
Measured. Calculated. 
AG Rape PO AMR SSS WARE Ne yc bars bards 42° Aisa: 
t: iv Sea eee ee ST OA cate AS tard ec katie ce act 22° 20° 3614 ' 
tev | EEE SEM Yo 2 Gan tap ire 36° oak Ge 
UP ARE Gs Ss Gy PCY E <r 16° Tom 20% 
Usv Syirt See eee oho iA PORE 
Uevv SOIT EOLA Ee er Bee eGo! 
TIOAVAGC cme ZIRT SON TOL Y=... kale ee cic wae oie ne 30° Baqmees 
The surfaces of the crystal planes on these crystals are, in gen- 
eral, flat and bright and of uniform lustre. They are, however, more 
or less irregularly marked similar to the planes shown in Fig. 2, 
Pl. xxvii, and reéntrant angles resulting from abortive terminations 
often occur. While the crystals are often doubly terminated, as 
illustrated in the figure, more commonly only about half of the com- 
plete crystal form is present, the plane of attachment being a rhom- 
bohedral or a basal plane. Numerous planes of rhombohedral cleav- 
age pass through the crystals, and the light reflected from them often 
brilliantly illuminates the interior. Many crystals are also often iri- 
descent from interference colors produced by parting along cleavage 
planes. Irregularly shaped grains of marcasite from one to two milli- 
meters in diameter often occur scattered through the outer layers of 
the crystals. Other associated minerals, often well crystallized and 
found more or less in contact, are galena, dolomite and chalcopyrite. 
A group of this character, now in the Museum collection, is shown in 
the frontispiece. 
*The letters used are Dana’s. 
