336                          MINERAL RESOURCES, 1914----PART II.
	in August. There was a slight increase in the output of turquoise and turquoise matrix, probably to meet the increased demand for souvenir gems in the western tourist trade. The table of production represents only an approximation of the output of gems in the United States. For many gems the values given in 1914 and in previous years have been estimated from figures showing the quantity pro­duced. That is, the tables give as nearly as possible the first values of the rough minerals. The value of the finished gems is several times greater. The preparation of complete statistics of production of precious stones is practically impossible, owing to the attitude assumed by some of the gem miners and dealers, who hesitate to furnish statements of production. The assistance of those who have kindly furnished such figures is greatly appreciated, and it is hoped that those who have not cooperated in this way in the past will do so in the future, on realizing that statistical information furnished by them will be held confidential. Under miscellaneous gems in the table of production for 1914 are included obsidian, beach pebbles, fossil coral, apatite, kyanite, and Iceland spar. During other years datolite, natrolite, pectolite, apophyllite, iolite, chondrodite, and various gem minerals with trade names have been included.