GEOLOGY IN NATIONAL MUSEUM MERRILL. 293 



50-carat white topaz from Japan, the 155-carat blue topaz from the 

 Russian Urals, and a series of uncut diamonds from Arkansas, se- 

 lected to show the natural crystal forms and the variation in color. 



It may be added that in building up the collection an attempt has 

 been made to show the possibilities of commonplace material; that 

 there is a goodly number of stones, in themselves of little intrinsic 

 value, which when properly cut and mounted are not merely beauti- 

 ful, but have the additional value of being out of the line of the usual 

 material sold in shops. In this connection particular attention may 

 be called to the cabochons of silicified wood, obsidian, epidotic granite 

 (unakite), and green feldspar (amazonstone). 3 



SECTION OF ECONOMIC GEOLOGY. 



EAST WING, SECOND FLOOR, EAST END AND NORTH SIDE. 



The mineral collection merges at the east end of the hall into that 

 of economic geology, under which name are comprised only those 

 minerals which have some economic value, either in their natural 

 condition or as sources from which valuable substances may be de- 

 rived. These collections are divided into two series, metallic and non- 

 metallic. The metallic begins with a flat top case containing excep- 

 tionally fine crystalline aggregates of gold and silver (pi. 17, fig. 1) . Of 

 historical interest in this case is a minute flake of gold, the identical 

 piece found by John Marshall in the mill race at Sutter's Fort in 

 1848, and by him hammered out to determine its nature. The fol- 

 lowing is a transcript of a letter accompanying it and which guar- 

 antees its authenticity. 



San Francisco, August 23, 18J/S. 



This paper contains the first piece of gold ever discovered in the northern 

 part of Upper California. It was found in February, 184S, by James W. Mar- 

 shall in the race of Capt. Jno. A. Sutter's sawmill about 45 miles from Sutter's 

 Fort, on the south branch of the American Fork. It was beaten out with a 

 hammer by Mr. Marshall, to test its malleability. 



It is presented to the National Institute, Washington, D. C. 



J. L. Folsom, 

 Captain, Assistant Quartermaster. 



Among other objects of unusual interest are a cube of iron pyrites 

 carrying crystallized gold and galena from near Juneau, Alaska; 

 several clusters and groups of gold and silver crystals, and an un- 

 usually large (444 grams) waterworn platinum nugget from Mjni 

 Tagilsk, Russia (pi. 18, fig. 1). Immediately adjacent to this case is 

 the large mass of native copper, weighing approximately 3,000 

 pounds, brought in 1873 from the Lake Superior region (pi. 18, 

 fig. 2), and large pieces of amygdaloid and breccia, showing impreg- 



8 For details of this collection, see Bulletin 118, U. S. National Museum, 1922. 

 101257—22— — 20 



