146 REPORT UNITED STATES GEOLOGICAL SURVEY. 



Analyses: 



(1.) (2..) 



Per cent. Per cent. 



An 1.38 1.53 



Ag i 0.25 0.25 



Te 55.86 55.54 



SiOa 34.72 35.91 



AI2O3, Fe2 03 6.15 6.14 



MgO.----. : ......... 0.17 0.19 



CaO ........................... 0.48 0.26 



Total .........^-...........99.01 99.82 



Magnesite. — In small quantities in the Running lode at Black Hawk. 



Magnetic Iron. — Bear Creek, Ralston Creek, Grape Creek. 



Magnetite. — In loose nodules on Gunnell and Procer Hills, at Central ; 

 in small octabedric crystals in the gneissic rock on station 1. Occur- 

 ring in the granites of various localities, Silver Hills, White House^ 

 Capitol ; in the dolerite rocks generally. At Idaho and Caribou. Oc- 

 curs near Golden. Octahedral crystals on Quartz Hill, near Central! 

 On Grape Creek, near Canon City, is an extensive deposit of magne- 

 tite, which is mined as iron ore. 



Magnolite. — From the Keystone Mine. It occurs, according to Genth,* 

 in capilloid and acicular crystals. It is the result of decompositioii 

 of coloradoite, and has the formula Hg2, Te04. 



Malachite. — Is found as the result of decomposition of fahlerz aud other 

 minerals at the Dallas, Leavenworth, and other mines near Central j 

 at the No-Name, Caribou, Seven-Thirty, Fourth of July, and others: 

 at Caribou ; at some of the Georgetown mines ; at the Hardscrabble 

 mines, on Mount Princeton, and other localities ; at Crater Mountain, 

 in the mines of Fair Play and Elk Mountain district. Malachite lode, 

 Bear Creek, Gendhemas lode, Tucker's Gulch, Oro City, Cation City, 

 Pollock, Montezuma. Allen's copper mine, head of San Luis Yalley. 



Makcasite. — Philipps Mine, Fair Play. 



Melaconite. — Occurring at the Gunnell, Briggs, Leavitt, Leaven- 

 worth, and other mines near Central ; at the Unknown Mine, in Mont- 

 gomery, Tucker's Gulch, Jefferson County, Colorado. Pollock, Mos- 

 quito. 



MelanteritE. — On the dumps of the Wood, Dallas, and Kansas mines, 

 and others, near Central ; in the Sweet Home Mine. 



Mercury. — Native ; associated with mercury-telluride in the Sunshine 

 district, Boulder County. 



Mesitite.— Black Prince lode. Lump Gulch. 



Mesolite. — Golden, Colo., South Table Mountain. 



MisPiCKEL. — See Arsenopyrite. '- 



Minium. — Freeland Mine, Trail Creek, Georgetown, Central City. 

 Dutchman lode, San Juan district. 



Meteoric iron.— ^%e Iron. 



Molybdenite.— Leavitt mine, at Central; occurring in thread-like 

 veins in Silver Hills, near Fiiir Play, Boulder County. Douglass 

 Tunnell, Georgetown ; Alice Cary lode, San Juan district. 



MoLYRDiTE. — Alice Carey lode, San Juan district. 



MuscoyiTE. — In good crystals on Mount Ouray, and in the coarse- 

 grained granite near Caiion City ; throughout the granite and partly 

 in the schist rocks. Fine crystals from Topaz Buttes. 



Nagyagite. — Gold Hill. This mineral is rare, and its identity is 

 scarcely fully established. 



*'Zeit8chr. farKryst. and Min., P. Groth, vol. II, No. 1, 1877. ' 



