Ii! 
Dolomite. 
By Proressor H. Louts. 
Read befove the Society, March 1st, 1887. 
[ABSTRACT. ] 
1 aes is a most widely distributed mineral; it 
occurs as a frequent companion to metalliferous 
minerals in true fissure veins, and in huge stratified deposits 
which form the surface rock throughout large areas of the 
continent of Europe. Although noticed by mineralogists at 
a very early date, it escaped recognition as a definite 
mineral till about a century ago, and this might be ascribed 
to the similarity of its external characters to those of calcite 
or mountain limestone. 
In 1791, Chevalier Deodat de Dolomieu wrote to M. Picot 
de la Peyrouse a letter which was published in the then 
current volume of the ‘Observations et Memoirs sur la 
physique,” appearing under the following title: ‘On a class 
of Calcareous rocks effervescing but slightly with acids and 
phosphorescing on percussion.” Dolomieu stated that he 
