Home » categories » rare book library » Smith. Gems and Precious Stones.

Physical Properties

Physical Properties Page of 96 Physical Properties Text size:minus plus Restore normal size   Mail page  Print this page
GEMS AND PRECIOUS STONES.
7
The specific gravity was taken, using a delicate assay balance, and diluted alcohol as the liquid, suspending the stones in a platinum wire cage directly into the alcohol, which had a specific gravity of "872 when cooled to the normal temperature. The following results were obtained, using the metric system of weights :—
From these results we are justified in considering these gems as rubies, and they have been placed in the collection named as such.
In the Eussian Court at the London Exhibition of 1851 there was a beautiful stone labelled Phenacite, which is a silicate of glucina, and it is used in Eussia as a gem-stone. Experts' opinions differed as to whether this was the correct name for the specimen. The owner's permission was obtained, and the stone tested. On taking the specific gravity it was found to be 3'5. The specific gravity of phenacite being at the highest 3, it was at once proved not to be that mineral, and on further tests being applied it was found to be a topaz.
Electricity.
As a large number of gems develop this property more or less, it is of some importance in their discrimination.
Friction will develop electricity in the diamond and topaz most markedly. The diamond displays positive electricity whether it be polished or in its rough state. Other gems are positively electric in the polished state only, and only have the power of developing negative electricity when in their rough state.
This development of electricity in a mineral may be seen by its power of attracting or repelling a light pith pellet suspended by cotton, or better, by a silken cord from a glass rod; or a small piece of cotton wool suspended in the same manner will answer the purpose ; even a piece of paper will be attracted in this way.
Pyro-electricity, or that developed by heat, is very marked in some minerals ; tourmaline especially, when heated to not more than 150° C, and suspended by a silken thread, will behave like an electro-magnet, having
Physical Properties Page of 96 Physical Properties
Suggested Illustrations
Other Chapters you may find useful
Other Books on this topic
bullet Tag
This Page