MINERALOGY. 



115 



quently twinned crystals, which is 

 shown by re-entrant angles and 

 striations over the whole surface. It 

 appears deep purple at one end and 



VIEW IN QUARRY AT CHARLOTTES- 

 VILLE RESERVOIR 

 Showing pegmatite dike on the left and 

 interbedded hornblende schist on the 

 right in granite gneiss. 



nearly colorless at the other. Abont 

 5 miles west from the University, the 

 Charlottesville reservoir is situated 

 among hills of Archean granite gneiss. 

 Two amethysts were found loose a 

 little north of the reservoir. The bet- 

 ter piece is pale in color and shows 

 several pyramids capping one another. 

 Unfortunately it has many flaws. This 

 is the only amethyst I know of from 

 this locality, so the accidental find 

 remains to be explained. A curious 

 pale blue opalescent quartz occurs in 

 the granite gneiss area. The cause of 

 this color is an interesting problem. 

 Some years ago Prof. F. P. Dunning- 

 ton examined thin sections with the 

 microscope and always found crystal- 

 lites of rutile present. But according 

 to Dr. T. L. Watson much of perfectly 

 colorless Appalachian quartz shows 

 crystallites of rutile, so that minute 

 needles of rutile do not necessarily 

 give rise to blue color. At Roseland, 



in Nelson Co., blue quartz is an abund- 

 ant constituent of the pegmatite dike 

 that carries rutile and some ilmenite ; so 

 at any rate it is very closely associated 

 with titanium compounds. 



Limonite after pyrite : — On the 

 northwest outskirts of Charlottesville, 

 pseudomorphs of limonite after pyrite 

 are abundant in the soil. The pyrite 

 originally existed in Huronian mica 

 slate, which is now very much dis- 

 integrated. The form is the simple 

 cube, and some of the smaller crystals 

 are nearly perfect ; though the larger 

 ones are generally elongated. Pene- 

 tration twins of two or more individ- 

 uals are common, and the facial stria- 

 tions are often clearly shown. At Rio 

 on the Southern R. R., where the mica 

 slate is less decomposed, cubes were 

 found in the rock. This proves the 

 mica slate to have been the matrix. 



Near the Charlottesville reservoir 

 the minerals of the granite gneiss have 

 been differentiated and masses of 

 black scaly hornblende and plagioclase 

 feldspar can be obtained. Finally re- 

 sidual clay occurs both in granite 

 gneiss and mica schist regions. 



It is hoped that this brief account can 

 sometime be expanded so as to em- 

 brace Albemarle Co. as a whole, when 

 doubtless a greater number of species 

 and more interesting occurrences can 

 be recorded. 



THE OPAL. 



Ca mythological poem.) 

 A dewdrop came, with a spark of flame 



He had caught from the sun's last ray, 

 To a violet's breast, where he lay at rest 



'Till the hours brought back the day. 



The rose looked down, with a blush and 

 frown; 

 But she smiled, all at once, to view 

 Her own bright form, with its coloring 

 warm. 

 Reflected back by the dew. 



Then the stranger took a stolen look 



At the sky so soft and blue; 

 And a leaflet green, with a silvery sheen, 



Was seen by the idler too. 



A cold north wind, as he thus reclined, 



Of a sudden raged around, 

 And a maiden fair, who was walking there, 



Next morning an opal found. 



[The above poem was found among some 

 torn leaves of a book on gems in mythology, 

 but the real name of the book or its author 

 could not be learned. — Editor.] 



