'Antonio Alzate. " 



383 



Me but always large from ten to one hundred feet, about 

 twenty-five feet being the most common. Some croppingsrun 

 without any interruption for several hundred feet (from 600 

 to 1500) and so close are the deposits or grottes one to the 

 other as to admit of many being worked by only one quarry. 



The deposits on the road to Cuencame are very numerous 

 and close together. One group covers an area of two hundred 

 acres, there being besides many others separated enough to 

 be considered apart. Less extensive are the deposits east of 

 the railway but also extensive enough to admit work of any 

 capacity. In the barranca de "Las Viboras," four miles from 

 Noria Station, one of the pockets should give with a little ex- 

 pense more than 200,000 cubic feet, considering only the su- 

 perficial deposits. Some of those of Pozo de Calvo, three mi- 

 les from Noria, should give also many thousands of cubic feet 

 on the surface of good onyx in very large pieces. 



The position of deposits on the flanks of the mountains 

 near or at the base and on the slopes of the hills is also wor- 

 thy of notice. Croppings rise up to the general rocky surface 

 which facilitates the opening of quarries without much barren 

 work and obtaining good profit from the beginniug of work. 

 The fissures that separate the blocks or tablets of onyx in 

 some of the deposits are almost vertical and this renders easy 

 their extraction, giving pieces with minimum thickness of 

 fifteen inches. The common size of blocks that can be got 

 here is similar to that of other onyx deposits of Mexico, a fair 

 average could be placed at twenty inches thick by four feet 

 broad and five feet long. Very often blocks larger than thirty- 

 five cubic feet are encountered. I saw in the small prospec- 

 ting works of "Las Viboras," enormous pieces, several of five 

 tons weight, of onyx marble of splendid honey -yellow colour. 



We cut from various places many samples in order to have 

 some idea of the very many different coloured varieties of onyx 

 and in some deposits, of these as large pieces can be obtained 



