PREFACE.
	In none of the numerous works on Mineralogy that have lately been published, have Gems been treated in a manner commensurate with the important rank which they hold in the mineral kingdom. The author of this treatise published in 1838 a small work on Gems, which was well received by the scientific world. As that edition was soon disposed of, the author intended to issue a larger and improved edition, but close application to his legitimate pursuits prevented him from accomplishing that object. In 1851 he visited the London Exhibition, where the treasures of the mineral kingdom, and the profusion of brilliant and costly gems from all quarters of the globe, formed a collection such as had never before been wit­nessed ; and he then resolved to embody the facts which he had there collected in a new work on Gems, which he has been encouraged to publish by the solicitations of numerous teachers and jewellers, who had used his former treatise as a work of reference, and who wish to have a work that will impart useful and correct information in regard to the locality and value of Gems in the present state of scientific knowledge. As a work on Gems would be incomplete without a treatise on Mineralogy, and as the author did not wish to enter into details foreign to his subject, he was at a loss how to commence ; but on consult­ing the recent works on the Elements of Mineralogy of Prof. Nichols and Zimmerman, he was convinced that a summary