140 
MANGANESE DEPOSITS OF INDIA: MINKRAI.OGY. [ ParT 1 : 
Manegaon example there is one section at right angles to the prism zone, 
showing two thin twinned lamellse bisecting the angles of the crossed 
cleavages. They indicate that the direction of twinning is parallel to h. 
Other microscopic characters worth noticing are the low birefringence, 
so that the colours are of the first order in thin sections ; and the 
absorption to be seen on relating the polarizer. 
Of the microscopic characters given above for this mineral the most 
Identification. serviceable in identifying it are its rose- 
pink colour ; its granular crystalline charac- 
ter, often causing it to resemble in appearance a crystalline limestone, 
except for its colour ; its hardness, so that it is scratched by a knife 
with difficulty or not at all ; its extraordinary toughness when massive, 
as nearly all the Indian specimens are, so that it is very difficult to 
prepare good hand- specimens of the rhodonite-rock ; and lastly its high 
specific gravity. As chemical tests, reactions for manganese and sHica 
must be relied on. At first sight it might be confounded with 
rhodochrosite on accoimt of its crystalline character and pink colour. 
The distinction between these two minerals is, however, easy to make, 
because rhodochrosite, being a carbonate, effervesces when heated with 
dilute hydrochloric acid, and is also much softer than rhodonite, being 
easUy scratched with a knife. 
The Indian rhodonites are not, however, always rose-pink in colour. 
At Guguldoho and Sitagondi, both in the Nagpur district, greenish grey 
rhodonite is to be found in massive pieces, whilst at Jothvad I found 
brown rhodonite, both these varieties being apparently fresh. It must 
be admitted that these two varieties have not been chemically examined, 
80 that the deduction based on their general aspect and appearance imder 
the microscope may be incorrect. When altered, rhodonite may show 
every shade of chocolate and dark brown up to brownish black and black. 
When Mallet's book on the Mineralogy of India was pubUshed 
in 1887 as Volume 4 of the Manual of 
Occurrence of rhodonite. ^j^^ Geology of India, only two occurrences 
of this mineral in India were known. One of these was a specimen 
obtained by Mallet from a hhari, who found a quantity of it a 
foot or two below the surface in the southern part of the Mirzapur 
district, United Provinces. The other was the occurrence of rhodonite 
in association with braunite at Mansar near Ramtek in the Nagpur 
district, described by Mallet in a paper in the Rec. Geol. Sur. Ind., XII, 
page 73, (1879). An examination of the specimen in the Musevun from 
