216 FIELD CoLUMBIAN MuseuM—GEo.Locy, Volt. II. 
cherry-red of hematite. Like the ore to which the crystals are at- 
tached, and from which they probably do not differ essentially in 
composition, the crystals are hard and tough, the hardness being 6.5. 
To the naked eye the crystals appear of ordinary homogeneity and 
purity, but on polishing a surface and examining it with a moderate 
magnifying power, the homogeneous character disappears. A con- 
siderable number of inclusions is seen, indicating that the crystal is 
not of uniform composition. The inclusions are in the form of red- 
dish patches, usually with straight outlines, and often triangular or 
elongated in shape, or they appear as spots of tuberose, irregular 
character elevated above the surface. These inclusions probably in- 
dicate different stages in the process of alteration of the mineral, but 
just what is not known. An analysis of some of the crystals was 
made by Mr. H. W. Nichols, those selected for the purpose being such 
as appeared homogeneous. The analysis gave the following results: 
Fe, O5.0. BEG. hee hates a eee 97.26 
Fe Oe coor ei tee Gare ee Re ae 0.78 
HAs hace, Coa ose noe ae ee t.2E 
TY Qo as ee Oe a ee Trace 
Mg: Cyt ie. Es ah sr eh da Trace 
Oi Oo rsg le eh hi ce teen ne ara Ove 
Deo dla Sk belee nie Sate eeeuie ale ee ee 0.69 
I00.19 
Ore PLM We i ae Re AN SAL 0.1% 
100.02 
No lime, copper, manganese, or phosphorus were found, although 
looked for. The analysis shows that inclusions of other minerals 
occur in the martite, chiefly, however, compounds by alteration. 
Exactly what minerals the different compounds may represent it is 
impossible to say, but the following may be suggested as a reasonable 
constitution for the martite crystals: 

Heamatiter man: sme moeaethiny <a. cate eee 90.12 
LimOni ter Zie eset beeen ery ane 8.35 
PiyTitetcitaetae Pee Reet Pee Ir a. piste as ae azo) 
OuartZieg i foe mmbertes Meets cea s (oe eae Gyre 
100.01 
The presence of pyrite is indicated by the content of sulphur 
and an almost exact equivalent of Fe O. Moreover, the powder of 
mineral when heated gives off a slight sublimate of sulphur. If 
pyrite is present in small quantity in the martite crystals it is possi- 
ble that the martite is a pseudomorph after that mineral. Silliman,* 
however, states that he found nothing in his examination of 

#06. Ctl; 
