Warning: Several sections of your profile and favorites are being migrated today. We apologize for any inconvenience. Portal logo
Login/Register
Bactrian Gold Treasure from Afghanistan, coming soon....
/gemstones/goodchild-precious-stones/page_026 - 2
 

Ch. 3: Physical Properties of Gem Stones

Ch. 2: Precious Stones, Modes of Origin Page of 311 Ch. 3: Physical Properties of Gem Stones Text size:minus plus Restore normal size   Mail page  Print this page
CHAPTER III.
THE PHYSICAL PROPERTIES OF GEM STONES.
I. The most important group of physical properties we have to deal with is that dependent on light. When light acts on a gem it may—
A.  Be reflected back again.
B.  Be transmitted.
C.  Produce phosphorescence.
A. When light is reflected from a mineral two phenomena may be observed—
a.   Colour.
b.  Lustre.
a. White light falling on a mineral and suffering reflec­tion may reveal a certain colour of the stone. This is due to certain of the components of the white light being held back or absoi'bed by the substance, while others of the coloured rays are returned to the eye and there produce a sensation of colour. Sbould a stone reflect all the rays of white light in the same proportion as it receives them it will appear white ; if all or nearly all the rays are stopped it appears black ; if all but the green rays are stopped we should say the stone was green, and so on. It is very unsafe to place much reliance on colour in the identification of precious stones, as in many cases one mineral may occur in several different colours, and on the other hand stones of
Ch. 2: Precious Stones, Modes of Origin Page of 311 Ch. 3: Physical Properties of Gem Stones
Suggested Illustrations
Other Chapters you may find useful
Other Books on this topic
bullet Tag
This Page