[ S9i ] 
“ Metal is fo difguifed and enveloped with other 
“ mineral Subftances, Juices, and Stones, that, for 
“ their Separation from the Gold, they are obliged 
“ to ufe Quickfilver. Sometimes they find mineral 
“ Subftances, which, from their being mixed with 
“ Tlatina , they chufe to negled. This Tlatma 
<e is a Stone (Tiedra) of fuch Rcfiftance, that it 
“ is not cafily broken by a Blow upon an Anvil. 
“ It is not iubdued by Calcination j and it is very 
“ difficult to extra a the Metal it contains even with 
“ much Labour and Expcnce.” 
In the before- mention’d Work, Chap. 1 1, the fame 
Author, when fpeaking of the remaining Works of 
the Indians of old, fays, “ the Specula wrought 
“ out of Stones, which are found in the Places of 
“ Worlhip of the Indians , are of two kinds, in re^ 
“ lation to the Matter of which they are made; 
“ One of thefe is call’d Tiedra de Inga, the other 
tl Tit dr a de Gallinazo. The firft of thefe is fmooth, _ 
“ of a leaden Colour, and not tranfparent $ they are 
“ ufuall'y found wrought of a circular Figure : One 
“ of the Surfaces is plain, and as fmooth as though 
11 it were made of a kind of Chryftal the other Sur- 
“ face is oval, or rather fomewhat fpherical, and not 
“ fo much burnilh’d as the plain one. Although they 
“ vary in their Size, they are commonly from three 
“ to four Inches in Diameter ; but he has feen one 
“ that was a Foot and half in Diameter. Its prin- 
“ cipal Surface was concave, and much augmented 
“ the Size of Objeds, as its Polifh was in as great 
li Perfedion as though it had been work’d by a dex- 
“ trous Artift in thefe Times, 
“ This 
