Vol. 58. CRYSTALLINE LIMESTONES OF CEYLON. 419 
variety of limestone occurring in the western pit, forming a 
handsome dolomite-clinohumite rock: other minerals present in 
small quantity are olivine(?) and blue spinel. Other varieties of 
limestone in the same pit are quite without clinchumite, and have 
different accessory minerals, or none. ‘The clinohumite forms large 
crystals with some approach to crystalline form, reaching | inch 
in longest diameter; smaller granular crystals are abundant. 
These are very diminutive, but have sometimes numerous well- 
developed crystalline faces. The grains are about twice as long as 
broad and slightly flattened. Examined between crossed nicols, 
they are found to extinguish always parallel to their length. 
whether lying on one side or on the other, whence it follows that 
they are elongated in the direction of the orthodiagonal axis 4. In 
thin sections, it can be clearly seen that the axial plane is parallel 
to the elongation. The pleochroism is a fine orange-yellow, ¢ pale 
chrome-yellow, and b like ¢ or very slightly darker. Absorption 
a>b=2c. In thin sections, basal cleavage is seen parallel to the 
elongation ; isolated grains are also occasionally seamed by irre- 
gular cracks, more or less transverse to their length. 
Mr. G. F. Herbert Smith has kindly measured one of the tiny 
erystals from Gettembe,' and identified the forms 3 
¢(001)e,(107}e, (103) ¢,(101) 25(113)i,(014)2,(012)r,(129) r, (127) r6(125) r,(121) 
The measurements are quoted in the following table :— 
| 
| Observed. Calculated (Dana, 6th ed.). | 
| Form. — —A~— SS | 
<- Azimuth. | Distance. | Azimuth. Distance. | 
fe) i | ° 1 1 
Le 101 OU ewe. ba a 8 66 "9 Via 
9 ” 79 i oP) 3) | oe) ” | 
a9 a7 79 9 | ” ” ” ’ 
9° bP) 19 7 9 9 99 
Pea | 103 SS) S60 0G ty 60 12 
} 9 ” 60 7 99 ” ” I) 
Cars 107 Peeler mes ese 46 20 
Lt eres 113 4G 40, 68 30 AG 18 68 444 
pvr ae V9 Go: V7 54° 9 65 10 5A Ie 
| 6 7 | 538 59 at HEN a 
ieee 125 bole) 688 eis 68 9 
i ae ea a! Garage $855) U5 ts 85 25 
_ 65 17 85 22 ” ” ” rh) 
ues. 12 Go 1G |) .G0) 45 ae 60 42 
| | 62058) 6 0 ae 
te: 012 SO 70 87 90 0 70" 82 
| | 90 | 470" 30 Lae ae 
ee 3... | | 014 90 11 54 40 ere 54 45 | 
* The determination of the mineral as clinohumite depends on the crystal- 
measurements referred to. Without these it would have been necessary to 
speak vaguely of ‘chondrodite.’ The mineral which occurs sparingly at Ampitiya 
is probably identical with the Gettembe clinohumite. ; 
