270 



DISCOVERY 



A. Gems of the First Rank 



Hardness between 8 and lo. Consisting of pure carbon 

 or pure alumina, or with alumina predominating. Fine 

 specimens of very rare occurrence and of the highest value. 



1. Diamond. 3. Chrysoberyl. 



2. Corundum (ruby, 4. Spinel. 



sapphire, etc.). 



B. Gems of the Second Rank 



Hardness between 7 and 8 (except precious opal). Specific 

 gravity usually over 3. Silica a predominant constituent 

 In specimens of large size and of fairly frequent occurrence 

 Value generally less than stones of group A, but perfect speci- 

 mens are more highly priced than poorer specimens of group A 

 T. Zircon. 8. Tourmaline. 



6. Beryl (emerald, etc.). 9. Garnet. 



7. Topaz. 10. Precious opal. 



C. Gems of the Third Rank 



These are intermediate in character, between the true gems 

 and the semi-precious stones. Hardness between 6 and 7. 



with the idea of testing large deposits. These 

 machines were no doubt very useful for diamond- 

 bearing deposits where there was only a small per- 

 centage of heavy particles, viz. diamonds and garnets, 

 but on deposits such as are found in Ceylon thej^ 

 were not a very great success, as they were really 

 too accurate in their work and collected too large a 

 concentrate. The consequence was that the con- 

 centrate was too bulky to sort by hand, and ordinary 

 hand-basket washing had to be done so as to reduce the 

 bulk. The same photograph shows the machine in 

 the background, the small native carriers on the right 

 carrying the gravel to the machines, and the native 

 basket-washer in his pit of water, washing, with the 

 basket in the foreground. It was not an imcommon 

 occurrence to obtain half a bucketful (li gallons) of 

 dallam (imperfect gems and crystals of all kinds) per 

 working-day. This when sorted would give probably 



: :.i: I'L.i.N r.\iU'N, 



Specific gravity usually greater than 2 '5. With the exception 

 of turquoise, silica is a prominent constituent of all these stones . 

 Value usually not very great, only fine specimens of a few mem- 

 bers of the group (cordierite, chrysolite, turquoise) have any 

 considerable value. Specimens worth cutting of comparatively 

 rare occurrence, others fairly frequent. 



Cordierite. 



Idocrase. 



Chrysolite. 



Axinite. 



Kvanite. 



16. 



17- 

 18. 



19- 

 20. 



Staurolite. 



Andalusite. 



Chiastolite. 



Epidote. 



Turquoise. 



Where the Machines failed 



Fig. 3 shows a small mechanical washing plant 

 in a rubber plantationjn Ceylon. This was erected 



one or two good specimens (generally sapphires), J to 

 I lb. of corundum crystals good enough for cheaper 

 ornaments or for crushing down for cutting-powder, 

 and the balance a mass of pretty glistening stones useful 

 for cheap ornaments. It is a question why the'public 

 prefer glass ornaments when they could get a real crystal 

 from the residues of gem-washings. The cutting of 

 gems is not such an expensive operation as most people 

 think. A very few shillings will cut the stones of 

 average size to be ready for mounting. 



Water -work 



As in all granite-formations, there is an abundance 

 of water. This has been the prime power that has re- 



