338 Count de Bournon's Observations , &c. 
influence of the magnet, in proportion to the quantity of it con- 
tained in the mixture. Its presence may be easily detected, when 
the ore is pounded, by the appearance of a red powder, which 
shows itself in the middle of the black powder of the aforesaid 
ore. 
Among the specimens of iron ore from Gellivare, in Swedish 
Lapland, which were brought here by Mr. Swedenstierna, a 
very intelligent Swedish mineralogist, there were some, in which 
this cubic oxide of iron was so pure and unmixed, that they were 
not at all, or at least in a very slight degree, acted upon by the 
magnet ; but, that they really belonged to the species here treated 
of, might be plainly perceived, by pretty strongly marked striae 
upon the surface, which crossed each other at right angles, and 
were sometimes even seen within the substance. In other spe- 
cimens, the cubic oxide of iron was mixed, in greater or less pro- 
portion, with the octaedral kind ; and this latter became, in that 
case, less attractable, in proportion as the former species was 
more abundantly mixed with it. Those who have been accus- 
tomed to examine this species, and are in the habit of using a 
lens, (without which many interesting objects in mineralogy 
escape our observation,) may become capable of distinguishing 
it in the ore ; and this faculty may perhaps hereafter be of great 
importance, provided it should be found that the quality of the 
iron obtained from the ore, is affected by the abovementioned 
mixture. If we scratch with a knife such specimens as contain 
both the abovementioned species, we may, indeed, by the ap- 
pearance of a red powder, discover the particles of the cubic 
oxide, (which particles, if separated, would not be attractable,) 
and we may thereby, in some measure, estimate the proportion 
of the above oxide in the ore. 
