Notices of Memoirs — Tungsten Deposits of Essexvale. 375 



the end of that period a local syndicate extensively sampled some 

 thousands of tons of rubble and made trial crushings. The grade 

 was found to be just too Ioav for profitable working by the methods 

 then employed. During 1916, however, determined efforts have 

 been made by other workers to test the rubble of two restricted areas. 



Altogether about 85 tons of concentrate valued at £7,165 has 

 been marketed. The returns for 1916 are 1\ t° ns valued at £467. 

 This was produced by one worker with a few natives in a five-foot 

 rotary diamond washer, and by one man on another claim who hand- 

 picked rubble and recovered 1,600 lb. of wolframite. 



The prospecting done on a few reefs that have been opened has 

 nowhere been for more than a few feet below the surface. This may 

 be due chiefly to the fact that the deposit upon which serious 

 prospecting work has been undertaken is from its nature the least 

 likely to prove profitable. 



Geology. — The known tungsten-bearing tract of country occupies 

 the central portion of an irregularly oval mass of granite about 

 8 miles long and 5 miles across at the widest part. The long axis of 

 the mass trends north-west to south-east. This granite body forms 

 the floor of a wide depression which is traversed by two permanently 

 flowing streams, one of which is known as Fern Spruit. The 

 granite appears to pass beneath the surrounding rim of epidiorite and 

 felsite hills. The soil is a pale-red sandy loam. There are very few 

 exposures excepting in the streams and an occasional small but bold 

 granite kopje. The granite almost wherever seen is coarse-textured 

 and massive, that is, not schistose. It is a hornblende granite, and 

 is thus different from the large granite masses of Rhodesia. Patches 

 of epidiorite, probably inclusions of country rock, and dykes and 

 other bodies of felsite are occasionally encountered, particularly near 

 the eastern edge. 



The Reefs. — The tungsten reefs consist of greisen composed chiefly 

 of a soft greenish-yellow mica or of mica, fluorspar, topaz, and 

 secondary felspar. This rock weathers soft and rusty brown. The 

 greisen has arisen by the action of vapours on a porphyry or aplite 

 (fine-textured white granite free from hornblende and mica). With 

 the greisen of each reef is a variable amount of rather white glassy 

 quartz forming strings or large lenses in the greisen, and evidently 

 connected with the greisenization, that is, deposited at the same 

 time and by the same agency as the mica, fluorspar, topaz, tourmaline, 

 chlorite, wolframite, and scheelite of the greisen. 



The constant presence of the quartz lenses as part of the greisen 

 bodies is a great help in recognizing the presence of the greisen. 

 Those parts of the greisen which contain little or no quartz very 

 rarely crop out, and thus may easily escape discovery. No tungsten 

 reefs have been found without the quartz, although it is quite 

 conceivable that such exist. 



The quartz strings expand into lenses exceeding 20 feet in width, 

 and thus make low hillocks such as those at " The Eanche " home- 

 stead ; again two-thirds of a mile to the south-east of this, and at 

 the Native Church a mile and a half north-east of Essexvale Siding. 



The reefs vary from 200 yards to about a mile long. The two 



