NGC Precious Metal & Bullion Standards 3 — Questions and Answers
Question 1: What is the troy weight of one standard U.S. 'Good Delivery' gold bar as traded on the COMEX exchange?
- 50 troy ounces
- 100 troy ounces
- 400 troy ounces (Correct answer)
- 1000 troy ounces
Correct answer: 400 troy ounces
The standard COMEX Good Delivery gold bar weighs approximately 400 troy ounces (about 27.4 pounds).
Question 2: What is 'coin silver' and what is its standard fineness in the United States?
- Silver mined from coin deposits, .800 fine
- An alloy historically used for U.S. coins, .900 fine (Correct answer)
- Pure silver used only in commemorative coins, .999 fine
- Silver alloyed with nickel, .925 fine
Correct answer: An alloy historically used for U.S. coins, .900 fine
Coin silver refers to the .900 fine silver alloy (90% silver, 10% copper) historically used in U.S. dimes, quarters, and half dollars before 1965.
Question 3: The specific gravity of pure gold is approximately:
- 10.5
- 15.3
- 19.3 (Correct answer)
- 21.4
Correct answer: 19.3
Pure gold has a specific gravity (density relative to water) of approximately 19.3 g/cm³, one of the highest of all metals.
Question 4: What does the term 'electrum' refer to in the context of precious metals history?
- An early electric refining process for gold
- A naturally occurring alloy of gold and silver (Correct answer)
- A platinum-gold alloy used in ancient coins
- The first silver standard established in ancient Greece
Correct answer: A naturally occurring alloy of gold and silver
Electrum is a naturally occurring alloy of gold and silver (with trace metals) that was used to make the world's earliest known coins in ancient Lydia.
Question 5: In the Golconda diamond grading standard used by NGC, what characteristic primarily defines a 'Golconda' classification?
- Origin from the Golconda mines of India only
- Exceptional transparency and absence of nitrogen (Correct answer)
- A specific minimum carat weight
- A unique crystalline structure
Correct answer: Exceptional transparency and absence of nitrogen
Golconda diamonds are classified by their exceptional transparency and near-absence of nitrogen, giving them a pure 'water-like' appearance.
Question 6: Silver tarnishes primarily due to reaction with which atmospheric compound?
- Oxygen (O₂)
- Carbon dioxide (CO₂)
- Hydrogen sulfide (H₂S) (Correct answer)
- Nitrogen (N₂)
Correct answer: Hydrogen sulfide (H₂S)
Silver reacts with hydrogen sulfide (H₂S) present in the atmosphere to form black silver sulfide (Ag₂S), which is the primary cause of tarnish.
Question 7: What is the standard fineness of the Canadian Silver Maple Leaf bullion coin?
- .925
- .950
- .999
- .9999 (Correct answer)
Correct answer: .9999
The Canadian Silver Maple Leaf is struck to a fineness of .9999 (99.99% pure silver), making it among the purest silver bullion coins in the world.
NGC Precious Metal & Bullion Standards 3
What is the troy weight of one standard U.S. 'Good Delivery' gold bar as traded on the COMEX exchange?