mineralogy. 4 g 
a black or blacklfh brown powder, and 
alfo of the fame colour in the fircp Howev^er^ 
when this iron ore contains only a Yery fmall 
quantity of iron, it may be ufed to make lime $ 
though it becomes of a grey colour, juft as whem 
clay is mixed with limeftone, as is the Alfwarften^ 
in which there is always fome mixture. 
It feems as if the white iron ore might be ufed 
with advantage, and preferably to others^ im 
making cement, whofe conftituent parts are at* 
ways lime and iron ^ but neither is it apt to con- 
crete, when once mouldered •, nor by experiments 
made for that purpofe, has It difcovered any qua* 
lity of binding or uniting ? we muft, therefore^ 
examine other fubftances, which may better an- 
fwer the intention and then it will be found, thafe 
iron, which is too much in its metallic ftate« i§ 
cafily affefted by the vitriolic acid, whereby the 
cement made of it would in length of time 
diflblved, and rendered ufelefs ^ nor, on the con- 
trary, is a perfeftly calcined iron of fo much fer- 
vice, as when it has fome of its phlogifton lefc 
For inftance, a cement prepared from the flags of 
a fmith’s forge, mixed with lime and coarfe land^ 
has been found, in fome refpeift, to anfwer all the 
good efte6ls expected, it depending only on time 
to fliew, if it is durable enough. The 
Ptizzolana and terras are nothing elfe than iron 
ores mixed with a yet unknown earth. Its effefL 
however, in the cement, may, perhaps, depend 
only on the iron, which has been reduced into i 
particular fubftance by means of fubterraneous 
fires, for their native places retain evident- figns 
thereof. 
If the flate in Henneberg, or Kinnekulle 
in the province of Wettcrgottland, ftiould 
happen 
