THE NONMETALLIC MINERALS. 225 



color. The larger coriindums are often injected with elongated, par- 

 allel-lying clusters or groups of the iron ores, as shown in fig. 3, Tscher- 

 mak's paper. The corundums in turn are often surrounded by borders 

 of ver}^ niiiuite zircons. The iron ore, as noted above, is principally 

 magnetite, ])ut which, by hydration and oxidation, has given rise 

 to abundant limonite. The magnetites are in the form of rounded 

 granules and dust-like particles, and also at times in well-defined octa- 

 hedrons. In their turn the magnetites also inclose particles of corun- 

 dum very much as the metallic iron of meteorites of the pallosite group 

 inclose the olivines and as shown in Plate 9, fig. 4. The iron ores, 

 as a rule, occur in parallel layers and lenticular masses or nests. 



The following account of these deposits and the method of working 

 is by A. Gobantz:^ 



Naxos, the largest of the Cyclades Islands, is remarkable as being one of the few 

 localities in the world producing emery on a large scale; the deposits, which are of 

 an irregularly bedded or lenticular form, being mostly concentrated on the moun- 

 tains at the northerii end of the island, the most important ones being in the imme- 

 diate vicinity of the village of Bothris. The island is principally made up of 

 archfean rocks, divisible into gneiss and schist formations, the latter consisting of 

 mica schists alternating with crystalline limestones. The lenticular masses of 

 emery, which are very variable in size, ranging in length from a few feet to 

 upward of 100 yards and in maximum thickness from 5 to 50 yards, are closely 

 associated with the limestones, and, as they follow their undulations, they vary very 

 much in position, lying at all kinds of slope, from horizontal to nearly vertical. 

 Seventeen different deposits have been discovered and worked at different times. 

 These range over considerable heights from 180 to 700 meters above sea-level, the 

 largest working, that of Malia, being one of the lowest. This important deposit 

 covers an area of more than 30,000 square metres, extending for about 500 metres 

 in length with a height of more than 50 metres. This was worked during the 

 Turkish occupation, and it has supplied fully one-half of all the emery exported 

 since the formation of the Greek Kingdom. The highest quality of mineral is 

 obtained from two comparatively thin but extensive deposits at Aspalanthropo and 

 Kakoryakos, which are 435 metres above the sea level. The mineral is stratified 

 in thin bands from 1 to 2 feet in thickness, crossed by two other systems of divisional 

 planes so that it breaks into nearly cubical blocks in the working. The floor of 

 the deposit is invaria1)ly crystalline limestone, and the roof a loosely crystalline dolo- 

 mite covered l)y mica schist. The underlying limestones are often penetrated by 

 dykes of tourmaline granite, which probably have some intimate connection with 

 the origin of the emery beds above them. 



Mineralogically emery is a compact mixture of blue corundum and magnetic iron 

 ore, its value as an abrasive material increasing with the proportion of the former 

 constituent. This proportion has, however, been usually much overestimated. 

 Seven samples collected by the author have been examined at the Technical High 

 School in Vienna, and found to contain from 60 to 66 per cent of alumina. The 

 average composition may be considered to l)e | corundum, the remainder being 

 magnetite and silica in the proportion of about 2 to 1, with some carbonate of lime. 



The working of the deposits is conducted in an extremely primitive fashion. 



1 Oesterreichische Zeitschrift fiir Berg- und Hiittenwesen, XLII, p. 143. Abstract 

 in the Minutes and Proceedings of the Institute of Civil Engineers, CXVII, pp. 

 466-468. 



NAT MUS 99 15 



