18«7.| ^"^ [Genth. 



100.00 — 100.07 — 100.21 — 100.38 — 99.43 — 100.40 — 99.36 



6. Yellow variety . — It occurs like the red in imitative shapes, and evi- 

 dently liiisbeen formed under similar conditions. 



The color is from a pale brownish- yellow, honey yellow to a reddish brown, 

 sometimes greenish-yellow, variegated in bands of paler and darker colors. 

 Globular, reniform, frequently ctirved lamellar, in many cases the laminae 

 readily separating. Several of the reniform masses from 25 to 35™™ in 

 size are really stalactites whicli have formed upon some unknown irregu- 

 larly shaped substance which has weathered out, leaving a cavity, others 

 are fiat and have deposited upon quartz, of which some remnants may 

 often be seen. Fibrous, radiating. 



The most interesting and apparently purest specimens came from Mina 

 Varosa ; it is also associated with the red varietj' in the Placer ores No. 

 6, rarely in microscopic botryoidal concretions in the sand from Mr. 

 Schlemm, and also in the ores of the San Antonio mine, forming about 

 one-fifih of the whole mass. 



The following analyses have been made : 



1. Globular, radi.iting from the centre ;;j[powder cream color. Mina Va- 

 rosa, State of Durango, VII, a and b. 



2. Reniform and lamellar, concentrically fibrous ; powder cream color. 

 Mina Varosa, VIII. 



3. Flat, brownish-yellow, banded, fibrous, radiating, powder dark cream 

 color ; from the Placer ores No. 6, IX. 



4. Laminated, reniform, fibrous, brownish-yellow ; powder brownish 

 cream color ; from Dr. Joseph Leidy,^X. 



VII. VIII. IX. X. 



