182 Mr. Howard's Experiments and Observations 
grain, having a small degree of lustre, resembling in some 
measure that of enamel. Their hardness is such, that, being 
rubbed upon glass, they act upon it in a slight degree; this 
action is sufficient to take off its polish, but not to cut it: they 
give faint sparks, when struck with steel. 
Another of these substances, is a martial pyrites, of an inde- 
terminate form : itsxolour is a reddish yellow, slightly inclining 
to the colour of nickel, or to that of artificial pyrites. The 
texture of this substance is granulated, and not very strongly 
connected : when powdered, it is of a black colour. This pyrites 
is not attractable by the magnet ; and is irregularly distributed 
through the substance of the stone. 
The third of these substances consists in small particles of 
iron, in a perfectly metallic state, so that they may easily be 
flattened or extended, by means of a hammer. These particles 
give to the whole mass of the stone, the property of being 
attractable by the magnet ; they are, however, in less propor- 
tion than those of pyrites just mentioned. When a piece of the 
stone was powdered, and the particles of iron separated from it, 
as accurately as possible, by means of a magnet, they appeared 
to compose about of the whole weight of the stone. 
The three substances just described, are united together 
by means of a fourth, which is nearly of an earthy consistence. 
For this reason, it is easy to separate, with the point of a knife, 
or even with the nail, the little globular bodies above mentioned, 
or any other of the constituent parts of the stone we may wish 
to obtain. Indeed the stone itself may readily be broken, merely 
by the action of the fingers. The colour of this fourth substance, 
which serves as a kind of cement to unite the others, is a 
whitish gray. 
