Gemstone (L6) Flashcards
What is the study of gems referred to as?
gemology
Gemstone is a collective term for _____
all objects used with ornamental stones for personal adornment
What is a “gem”
a gemstone that has bveen cut to show its beauty
The 2 main categories of Gemstones?
Precious gemstones and Semiprecious gemstones
What are the 3 qualities that the value of most gemstones (precious or semiprecious) are based on?
Beauty
Durability
Stability
What is the quality “Beauty”
bsed on one or a combination of the qualities of color, lustre, transparency (or clarity), or enhanced optical properties due to cutting and fashioning
What is the total breakdown of how the gemstone’s value is judged
50-60% quality of color
20-30% clarity
10-20% on the cut of the finished stone
The 4 C’s used to determine the value of gems?
Carat weight, Color, Clarity, and Cut
What does Durability refer to?
The resistance of a gemstone to damage
What are2 of the main properties influencing the durability of a gemstone?
Hardness and Tenacity
What is Tenacity?
the resistance to bending and breaking (diff from hardness)
What does Stability refer to?
A gem’s resistance to destruction by chemical factors
or how well a gemstone retains its colour
What are the 3 main additional factors influencing the value of a gemstone?
Weightr, Rarity, and Demand
What standard unit of weight is used in the pricing of gemstones?
Carat (ct)
1 ct = 0.2 grams
Where does the name Carat come from?
comes from the carob bean and in the old days, the weight of a gem would be measured equivalent to the weight of carob seeds
What must you bear in mind when using the Carat measurement?
It must be applied within the particular gemston as the size of gem varys among different stones
What should you use instead of carat weight when looking for the setting a particular gemstone?
the stone’s dimensions in mm
What is the largest uncut diamond in the world?
Cullinan Diamond
What was the largest stone cut from the original Culinan stone
Cullunan 1 (The Great Star of Africa)
Where was the SECOND largest gem-grade diamond discovered?
Botswana
What was the gem discovered in Botswana made into?
The Graff Lesedi Le Rona (largest emerald cut diamond in the world)
What does “Rarity” refer to?
the exceptional nature of the natural geological processes that form them
How can certain gemstone values fluctuate?
Depending on the trends in fashion
Why was there misinformation regarding gems and their relationships?
because of the ancient practice of grouping precious stones by color rather than mineral makeup
gemstone quality mineral of a single mineral can be given diff names if they are of diff color. T or F
T
When corundum contains a sufficient quanitity of chromium, what happens and what is it called?
it exhibits a deep red color and is called “Ruby”
When corrundum exhibits any color other than red, what is it called?
Sapphire
What is Asterism and how is it created?
it is a star pattern in gems and results from the presence of the mineral rutile within the crystal
What is emerald?
the green variety of beryl
What is Aquamarine?
the light blue variety of beryl
What are the 3 basic cuts used?
The Cabochon
The Brilliant Cut
The Step (Trap) Cut
What is a Cabochon and where is it used in?
a cut that is basically a simple round-to oval shape
used in translucent (clouded) and opaque gemstones with bold colors and low-intermediate harndess
Brilliant Cut? and what is it used for?
this round cut accentuates a gemstones ability to transmit, reflect, and disperse light, and used for diamonds
The Step Cut and where is used?
has a broad table-like central facet surrounding by smaller and longer rectangular facets around its corners
emphasizes the color of the stones with a low degree of light dispersion
The emerald cut and why is it used?
special type fo step cut, with the corners lopped off
developed to reduce edge damage of emeralds with a brittle tenacity
