A copper penny is about 3.5 on the Mohs scale. Which of these minerals can it scratch?Answer: Calcite. Source: National Park Service: Mohs Hardness Scale
A fingernail will scratch gypsum but not calcite. Where does a fingernail stand on the Mohs scale?Answer: About 2.5. Source: National Park Service: Mohs Hardness Scale
A rock has no single hardness, because each mineral in it has its own. In a topaz-rich granite, which mineral is the softest?Answer: Mica. Source: Wikipedia: Mohs scale
A steel knife blade and a plate of glass have the same Mohs hardness. What is it?Answer: About 5.5. Source: National Park Service: Mohs Hardness Scale
A stone can be scratched with apatite, not with fluorite. Where does it stand on the Mohs scale?Answer: Between 4 and 5. Source: Wikipedia: Mohs scale
A streak plate of unglazed porcelain cannot test the hardest minerals. About how hard is the plate itself?Answer: About 7. Source: Wikipedia: Streak (mineralogy)
Besides geologists, which industry uses the Mohs scale, to test touch screens and cover glass?Answer: Electronics makers. Source: Wikipedia: Mohs scale
Garnet stands at 6.5 to 7.5. Which of these gems will it scratch if they rub together in a jewelry box?Answer: Opal. Source: GIA: January Birthstone
Gems softer than 7 scratch easily in everyday wear. What in ordinary dust and grit does the scratching?Answer: Silicon dioxide, as in quartz. Source: Wikipedia: Cabochon
Jade is not unusually hard, yet Stone Age people made axe heads of it. Which quality were they relying on?Answer: Toughness. Source: GIA Gem Encyclopedia: Jade
Sapphire has no cleavage, which helps it stand up to daily wear. What does a stone with cleavage tend to do?Answer: Break when it is struck. Source: GIA: September Birthstone
What is the only thing hard enough to scratch a diamond?Answer: Another diamond. Source: GIA Gem Encyclopedia: Diamond
Which gem mineral stands at 8 on the Mohs scale?Answer: Topaz. Source: USGS Natural Gemstones: Mineral Gemstones
Which mineral marks 7 on Mohs's scale of hardness?Answer: Quartz. Source: USGS Natural Gemstones: Mineral Gemstones
Which of these gems is the softest and the easiest to scratch?Answer: Pearl. Source: GIA: June Birthstones
Which organic gem does the USGS list as the softest, at 2 to 2.5 on the Mohs scale?Answer: Amber. Source: USGS Natural Gemstones: Organic Gemstones
What gems are made of 16
A star sapphire's star comes from fine needles of which mineral, known in the trade as silk?Answer: Rutile. Source: Wikipedia: Asterism (gemology)
Alexandrite is the color-change variety of which mineral?Answer: Chrysoberyl. Source: GIA Gem Encyclopedia: Alexandrite
Amber and copal are both fossil tree resin. What sets amber apart?Answer: It is far older, more than a million years old. Source: GIA: Amber Description
Besides lava and rock from deep in the mantle, where else has gem peridot been found?Answer: In meteorites. Source: GIA Gem Encyclopedia: Peridot
The electric blues and greens of Paraíba tourmaline come from traces of which metal?Answer: Copper. Source: GIA: October Birthstones
Jet, a velvet-black gem cut into beads, is a compact form of what?Answer: Coal. Source: USGS Natural Gemstones: Organic Gemstones
Lapis lazuli is a rock, not a single mineral. Which mineral makes its golden flecks?Answer: Pyrite. Source: GIA Gem Encyclopedia: Lapis Lazuli
Most citrine on the market began as which purple gem, turned yellow by heat?Answer: Amethyst. Source: GIA Gem Encyclopedia: Citrine
Pink morganite, golden heliodor and colorless goshenite are all varieties of which mineral?Answer: Beryl. Source: USGS Natural Gemstones: Mineral Gemstones
Ruby and sapphire are both the mineral corundum. What color is corundum in its purest form?Answer: Colorless. Source: GIA Gem Encyclopedia: Ruby
Traces of which element give spinel its most vivid blue?Answer: Cobalt. Source: GIA: Spinel Description
What does a technician put into a saltwater oyster to start a cultured pearl?Answer: A shell bead with a piece of mantle tissue. Source: GIA: June Birthstones
What makes the flashing play-of-color in a precious opal?Answer: Light bending between tiny stacked spheres of silica. Source: GIA Gem Encyclopedia: Opal
Which gem is the only one made of a single element?Answer: Diamond. Source: GIA: Diamond Description
Which two trace elements together turn corundum into blue sapphire?Answer: Iron and titanium. Source: GIA: Sapphire Description
Why is nearly all the blue topaz in jewelry blue?Answer: Colorless topaz was treated with radiation and heat. Source: GIA: November Birthstones
Famous stones 16
After ultraviolet light is switched off, the Hope Diamond goes on glowing for a while. In which color?Answer: Red. Source: Wikipedia: Hope Diamond
Before it was cut, the Black Star of Queensland, a star sapphire of 733 carats, spent about ten years in a family home as what?Answer: A doorstop. Source: Wikipedia: Black Star of Queensland
The Black Prince's Ruby in the Imperial State Crown is not a ruby. What is it?Answer: A red spinel. Source: GIA Gem Encyclopedia: Spinel
The Cullinan Diamond, found in 1905, weighed 3,106 carats in the rough. In which country was it found?Answer: South Africa. Source: Wikipedia: Cullinan Diamond
Cullinan I, the Great Star of Africa, weighs 530.4 carats. In which piece of the British regalia is it set?Answer: The Sovereign's Sceptre with Cross. Source: Wikipedia: Cullinan Diamond
The Dom Pedro, an obelisk of 10,363 carats at the Smithsonian, is cut from which gem?Answer: Aquamarine. Source: GIA: March Birthstones
The Dresden Green, a diamond of 41 carats, owes its apple-green color to what?Answer: Natural radiation. Source: Wikipedia: Dresden Green Diamond
The Hooker Emerald, 75.47 carats, once belonged to an Ottoman sultan. How did he wear it?Answer: In a belt buckle. Source: Wikipedia: Hooker Emerald Brooch
How did its last private owner send the Hope Diamond to the Smithsonian in 1958?Answer: By registered mail. Source: Wikipedia: Hope Diamond
How much does the Hope Diamond weigh?Answer: 45.52 carats. Source: Wikipedia: Hope Diamond
In which city is the Hope Diamond on permanent show?Answer: Washington, D.C. Source: Wikipedia: Hope Diamond
La Peregrina, a famous pear-shaped pearl, has a Spanish name. What does it mean?Answer: The pilgrim, or wanderer. Source: Wikipedia: La Peregrina pearl
The Olympic Australis, an opal of 17,000 carats, was found in South Australia in 1956. What is it named after?Answer: The Olympic Games held in Melbourne that year. Source: Wikipedia: Olympic Australis
The Shrine of the Three Kings in Cologne Cathedral holds 200 carats of gems long taken for emeralds. What are they?Answer: Peridots. Source: GIA: August Birthstones
The Star of India, a star sapphire of 563.35 carats, is kept at a natural history museum in which city?Answer: New York. Source: Wikipedia: Star of India (gem)
Where is the Koh-i-Noor diamond on public display?Answer: The Tower of London. Source: Wikipedia: Koh-i-Noor
Minerals at work 16
About 95 percent of titanium is used as titanium dioxide rather than as metal. What is titanium dioxide used as?Answer: A white pigment in paint, paper and plastics. Source: USGS: Titanium Statistics and Information
Barite takes its name from a Greek word meaning what?Answer: Heavy. Source: USGS: Barite Statistics and Information
Bauxite is the ore of which metal?Answer: Aluminum. Source: USGS: Bauxite and Alumina Statistics and Information
Garnet has been used since the Bronze Age as a gemstone and as what else?Answer: An abrasive. Source: GIA: January Birthstone
In nearly all quartz watches, how many times does the crystal vibrate each second?Answer: 32,768. Source: Wikipedia: Quartz clock
Magnetite and hematite are the main minerals of which ore?Answer: Iron ore. Source: USGS: Iron Ore Statistics and Information
Most gypsum used in the United States ends up in which building material?Answer: Wallboard. Source: USGS: Gypsum Statistics and Information
The oxide of the mineral zircon is made into which well-known diamond look-alike?Answer: Cubic zirconia. Source: USGS: Zirconium and Hafnium Statistics and Information
Salt is the raw material for making chlorine and which other industrial chemical?Answer: Caustic soda. Source: USGS: Salt Statistics and Information
Sardonyx was a favorite stone for the seals and signet rings of Rome. What made it so practical?Answer: Hot wax did not cling to it. Source: GIA: August Birthstones
Soapstone is an impure, massive form of which mineral?Answer: Talc. Source: USGS: Talc and Pyrophyllite Statistics and Information
Synthetic sapphire is tough enough for the windows of spacecraft. In which everyday machine does it also serve as a window?Answer: Supermarket scanners. Source: GIA Gem Encyclopedia: Sapphire
Tourmaline becomes electrically charged when it is heated, and also when it is what?Answer: Squeezed. Source: GIA Gem Encyclopedia: Tourmaline
Which red gem was at the heart of the first laser, built in 1960?Answer: Ruby. Source: GIA Gem Encyclopedia: Ruby
Which soft gray mineral, a form of carbon, goes into high-temperature lubricants and the brushes of electric motors?Answer: Graphite. Source: USGS: Graphite Statistics and Information
Why is a sliver of quartz used to keep time in a watch?Answer: An electric signal makes it vibrate at a steady rate. Source: Wikipedia: Quartz clock
Words of the trade 16
A carat is divided into 100 smaller units. What are they called?Answer: Points. Source: Wikipedia: Carat (mass)
Carat with a C weighs gems. What does karat with a K measure?Answer: The purity of gold. Source: Wikipedia: Fineness
Emerald dealers call the inclusions inside a stone its jardin. What does the French word mean?Answer: Garden. Source: GIA Gem Encyclopedia: Emerald
How many facets does a modern round brilliant diamond have, counting the culet?Answer: 58. Source: Wikipedia: Brilliant (gemstone cut)
How much is one carat, the unit used to weigh gems?Answer: 200 milligrams. Source: Wikipedia: Carat (mass)
How much of sterling silver is silver?Answer: 92.5 percent. Source: Wikipedia: Fineness
The name garnet comes from a medieval Latin word for which fruit, after the gem's red color?Answer: Pomegranate. Source: GIA: January Birthstone
Padparadscha, the name of a rare pinkish-orange sapphire, comes from the Sinhalese word for which flower?Answer: Lotus. Source: GIA: Sapphire History and Lore
What do gemologists call the star of light seen on some sapphires and rubies?Answer: Asterism. Source: Wikipedia: Asterism (gemology)
What do ruby dealers mean by pigeon's blood?Answer: The best color: deep red tinged with purple. Source: GIA: July Birthstone
What does a lapidary do?Answer: Cuts, polishes or engraves precious stones. Source: USGS Natural Gemstones: Key Terminology
What does the trade call the web of dark veins that runs through some turquoise?Answer: Matrix. Source: GIA Gem Encyclopedia: Turquoise
What is a cabochon?Answer: A gem shaped and polished smooth, not faceted. Source: Wikipedia: Cabochon
What is the culet of a cut diamond?Answer: A small facet at the very bottom. Source: Wikipedia: Facet
When American jewelers revised the birthstone list in 1952, which stone did zircon replace for December?Answer: Lapis lazuli. Source: Wikipedia: Birthstone
Which gem was added to the American list in 2016 as a birthstone for August?Answer: Spinel. Source: Wikipedia: Birthstone
How it works
Where, besides lava, has gem peridot turned up, and why did Romans favor sardonyx for their seals? These gem and mineral trivia questions and answers each show the reason and a link to the source.
Read the full guide
Questions and answers for trivia about gems and minerals
Hardness and the scratch scale tests stones with a fingernail and a copper penny. What gems are made of asks why sapphire is blue and what starts a cultured pearl. Famous stones has the Hope, the Cullinan and a sapphire once used as a doorstop.
Mineral trivia questions and answers for a rock club
Minerals at work follows gypsum into wallboard, barite into drilling mud and quartz into a watch. Words of the trade sorts carat from karat and explains cabochon, culet and pigeon's blood.
For a jewelry evening, play the gemstone trivia questions and answers of Famous stones and Words of the trade.
Questions and answers
What are some easy gemstone trivia questions?
Which gem is the only one made of a single element? What does karat with a K measure? In which city is the Hope Diamond shown? The answers are diamond, the purity of gold and Washington, D.C.
What are some diamond trivia questions?
What is the only thing hard enough to scratch a diamond? In which country was the Cullinan found? How many facets has a round brilliant? The answers are another diamond, South Africa and 58. Twelve of the 80 questions are about diamonds.
What is the difference between a carat and a karat?
A carat is a weight, used for gems: 200 milligrams, a fifth of a gram. A karat measures how pure gold is, counted in 24ths. British spelling uses carat for both.
What is the difference between a mineral and a gemstone?
By the U.S. Geological Survey's definitions, a mineral is any naturally formed, homogeneous inorganic material. A gemstone is a mineral, stone or organic matter that can be cut and polished for jewelry, so amber, pearl, coral and jet are gems but not minerals.
How were the answers checked?
On October 9, 2026, each on its linked page: the Gemological Institute of America (GIA) for 31, the U.S. Geological Survey for 15, the National Park Service for 3, Wikipedia for 31. Not affiliated with any.