KO.2220. COLORED VARIETIES OF QUARTZ— WATSOS d JJEARD. 555 



I. Princo Edward County, Virginia. Collected by William M. Thornton. Jr. Fiimi.shed by Prof 

 F. P. Dunnington, University of Virginia. 



II. Madison County, Montana. Furnished by Footo Mineral Company. 



III. Madison County, Montana. Furnished by Foote Mineral Company. 



IV. Brazil, South America. Furnished by Footc Mineral Company. 



V. Amazon claim, 3 miles north of Texas Creek, Colorado. Furnished by D. B. Stcrrctt through United 

 States National Museum. 



VI. South Dakota. Furnished by United States National Museum. Specimen without number. 



VII. Greenland. Furnished by United States National Museum. Cat. No. 95.S2. 



VIII. South Dakota. Furnished by United States National Museum. Cat. Ko. R4a85. 



IX. South Dakota. Furnished by United States National Museum. No number. 



X. Paris, Maine. Furnished by United States National Museum. Cat. No. 81302. 



XI. Southford, New Uaven County, Connecticut. Furnished by United States National Museum. 

 Cat. No. S6915. 



XII. New York (probably Bedford). Furnished by United States National Museum. Cat. No. 1R331. 



XIII. Rutile district, Nelson County, Virginia. 



As tabulated the figures disclose rather marked variation in each 

 of the constituents for both the amethyst and rose varieties of quartz. 

 When individual analyses are considered, it is observed that amethyst 

 contains tlie highest percentage each of manganous oxide (MnO) and 

 ferric (..vide (FCjO,), while rose quartz shows the highest percentage 

 of titanium dioxide (TiO,) and the lowest percentage each of manga- 

 nous oxide (MnO) and ferric oxide (FcoOj) . The average percentages 

 of the individual constituents determined for the two varieties of 

 quartz are as foUows: 



TiOo. MnO. Fe-Oi. 



Amethyst quartz 0. 002577 0. 000565 0. 000240 



Rose quartz 003185 . 000423 . 002735 



PETROGRAPHY. 



A tliin section was cut from each of the 12 specimens analyzed 

 (eight of rose quartz and four of amethyst) and studied micro- 

 scopically. In each thin section the quartz was colorless and 

 cxliibited the features common to vein quartz in general. Threo 

 of the sections of rose quartz and one of amethyst exhibited slight 

 to distinct wavy extinction, with optical disturbance not noted in 

 either of the other eight slides. Inclusions of varying nature, 

 chiefly mineral (sohd) but sometimes hquid, were developed in 

 each slide and in several they were fairly abundant. Their dis- 

 tribution was usuallj^ irregular but at times they wore partly arranged 

 in lines. 



The identity of most of the mineral inclusions could not be defi- 

 nitely established. With only one exception (ameth3'st), rutile in 

 the form of needle-hke inclusions was definitely determined as 

 being present. The rutile inclusions were more abundant in tho 

 rose quartz and were only sparingly present in three and entirely 

 absent from one of tho amxHhyst from Brazil (IV in table of analyses, 

 page 554) purchased from the Footo Mineral Company. The larger 

 average titanium content in the rose quartz is shown in tho table 

 of chemical analyses on page 555. The minute, dark-colored, dust- 

 like inclusions in both varieties of tho quartz were indeterminnto as 



