Curious questions
Does diamond burn? What is gold used for in space? Why is painite found only in Myanmar? The questions people ask most about stones, with sourced answers.
Amber
Does the word “electricity” come from amber?
Yes. The ancient Greek name for amber was “elektron”. Rubbed on wool, amber becomes charged and picks up small scraps of paper. In 1600 the English scientist William Gilbert named materials that attract objects when rubbed after this word, which is where the idea of “electricity” comes from.
Baryte
What does the white drink before a stomach X-ray have to do with a stone?
The substance in it comes from baryte: very pure baryte is used as a contrast agent in X-rays of the digestive system, because baryte blocks X-rays well. For the same reason it is used in hospitals and nuclear facilities to make heavy concrete that shields against radiation.
Bauxite
What stone are aluminium foil and drink cans made from?
Bauxite. According to İMİB, 90% of the world’s bauxite output is used to make aluminium. Light, durable and resistant to corrosion, aluminium is used in everything from packaging and construction to cars and transport.
Cassiterite
Why don’t tin cans rust? What does “tinning” mean?
Tinplate is steel coated with tin: steel surfaces are coated with tin so that they do not rust. Cassiterite is the main ore of tin. According to MTA, more than half of the tin produced over the last decade went into lead-free solder for the electronics industry, and bronze, its alloy with copper, gave its name to the Bronze Age.
Chalcopyrite
Where does the copper in electric cables come from?
Mostly from chalcopyrite. Chalcopyrite is the most important ore of copper; most of the copper produced in the world comes from this mineral. Copper, an excellent conductor of electricity and heat, is used in cables, electric motors, transformers and circuit boards.
Coal
Are coal and diamond the same thing? Does diamond form from coal?
Both are mostly carbon, but diamond does not form from coal. Coal is a sedimentary rock made from buried, heated plant remains, and coal seams are rarely buried deeper than a few kilometres. Diamonds form about 150–200 kilometres down, in the mantle, and most formed long before the land plants that made coal even existed.
Colemanite
How much of the world’s boron is in Türkiye?
According to USGS data, Türkiye is by far the first in the world for declared boron reserves; according to Eti Maden it holds about 73% of the world’s boron reserves. About 70% of Türkiye’s deposits are colemanite. Still, boron is a raw material for industries such as glass, ceramics, detergents and fertilisers, not an energy source like oil.
Diamond
Does diamond burn?
Yes. Diamond is pure carbon, so it can burn: in pure oxygen it ignites at about 690–840 °C and leaves only carbon dioxide behind. In 1772 Antoine Lavoisier focused sunlight through a lens onto a diamond, burned it and so proved that diamond is made of carbon. Diamond is not a “fireproof” stone.
Can a diamond break?
Yes. Diamond is very hard, meaning it does not scratch easily, but it is brittle and has perfect cleavage in four directions. A hard knock can chip or split it, and diamond cutters deliberately cleave stones along these planes.
Evil eye bead
Is the evil eye bead a stone?
No. Although many people think it is a stone, the evil eye bead is not a natural stone but a handmade glass bead. Rings of white, light blue and black glass are layered onto a dark blue glass body to make an eye; the dark blue comes from metal compounds such as cobalt added to the glass.
Fluorite
Is there stone in camera and telescope lenses?
In some, yes. Because fluorite splits light into colours very little, camera and telescope lenses are made from fluorite crystals grown artificially. Fluorite’s main uses, though, are in smelting steel and aluminium and in making hydrofluoric acid, the raw material of many fluorine compounds.
Gold
What is gold used for in space?
Very thin films of gold strongly reflect infrared light, that is, radiant heat. That is why gold is used as a heat shield in the sun visors of astronauts’ spacesuits and in the visors of heat-resistant suits. The 6.5-metre primary mirror of the James Webb Space Telescope is also made of beryllium coated with gold, so that it reflects infrared light well.
Does gold rust or tarnish?
No. Gold resists most acids and does not corrode or tarnish under ordinary conditions. Because of this durability and its good electrical conductivity, it is used in corrosion-resistant electrical connectors in all kinds of computerised devices, its chief industrial use.
Graphite
Is there lead in a pencil?
No. A pencil contains no lead at all: the core is made of a mixture of graphite and clay. The name “lead” survives from the time when graphite was mistaken for a lead ore. Like diamond, graphite is made of carbon, but it is soft and slippery.
Halite (rock salt)
Is rock salt the same as table salt?
Yes, it is the same substance: halite is the mineral made of sodium and chlorine, the same as the salt we put in food. When sea or lake water evaporates, the salt left behind crystallises as halite, and salt left by seas that dried up millions of years ago now forms thick layers of rock salt underground.
Hematite
What is the red paint in cave paintings?
Mostly iron oxides such as haematite. Red ochre, one of the oldest paints people used, gets its colour from haematite, and the red tones in prehistoric cave paintings mostly come from such iron oxides. Today haematite is, together with magnetite, the main mineral of iron ore.
Himalayan salt and salt lamps
Does a salt lamp clean the air?
No. Salt draws water vapour from the air (it is hygroscopic). The droplets that collect on the lamp are salty water made by moisture in the air wetting the salt; they do not show that the air is being cleaned.
Does Himalayan salt really come from the Himalayas?
No. This pink salt is mined in the Salt Range, a separate mountain range south of the Himalayas in Pakistan’s Punjab, especially at the Khewra salt mine. “Himalayan salt” is a marketing name.
Iron meteorite
Is a heavy black stone that attracts a magnet a meteorite?
Usually not. Most stones found this way and taken for meteorites are slag, pieces of cast iron or iron ores such as magnetite and haematite. A firm identification needs a nickel analysis and an expert examination.
Are meteorites hot when they land?
No, most land cold. During the short trip through the atmosphere only a thin outer layer melts and quickly cools; the inside, coming from the cold of space, has no time to heat up. According to NASA, most meteorites land cold and do not start fires.
Jade
Why does the most valuable jade come from Myanmar?
Most gem-quality jadeite comes from northern Myanmar; deposits of carving quality are found almost only there. The reason lies in how jadeite forms: only in subduction zones at continental margins, where rocks are transformed at very high pressure but relatively low temperature, and these conditions come together in very few places on Earth. The most valuable kind, “imperial jade”, is known for its intense emerald green, which comes from traces of chromium.
Kaolinite
What clay are porcelain and paper made with?
Kaolin. Made of the mineral kaolinite, kaolin is one of the main raw materials of porcelain and white ceramics, and it stays white when fired. It is also used as a filler inside paper and as a coating on its surface.
Marble
What happens if lemon juice or vinegar is spilled on marble?
Marble is made of calcite or dolomite, with a hardness of 3–4, and it reacts with acids. Acids such as lemon juice and vinegar quickly dull and etch its polished surface, so acidic spills on marble should be wiped up at once.
Meerschaum
Does meerschaum float on water?
Dry, porous pieces can float. Meerschaum (sepiolite) is a white, very light and porous clay mineral; it is soft when it comes out of the quarry damp and is easy to carve. Craftsmen in Eskişehir make pipes, prayer beads and ornaments from it.
Obsidian
Is obsidian used in surgery?
In some special operations, yes. An obsidian blade can have a much finer, sharper edge than a steel scalpel. But obsidian is brittle: its edge chips easily and the blade breaks if knocked, so obsidian scalpels are used only for certain special tasks.
Oltu stone
Is Oltu stone amber? What is “black amber”?
No. The name “black amber” is misleading: amber is fossilised tree resin, while Oltu stone is coalified wood; they are different substances. Oltu stone is a kind of jet; the world’s most famous jet source is Whitby in England.
Painite
Why is painite found only in Myanmar?
Painite contains both zirconium and boron, and these two elements very rarely come together in nature. So painite could only form under very special conditions: the area where it is known lies in an extremely small region around Mogok in Myanmar.
Why is painite so valuable?
Above all because it is so rare: until late 2004 only two painites had ever been cut into gems. Later searches at Mogok turned up thousands of new pieces, but most are cracked and full of inclusions, and very few are good enough to cut. Its hardness (Mohs 7.5–8), its transparency and its orange-red colour, which comes from chromium and vanadium, also make it attractive as a gem.
Pearl
Does a pearl dissolve in vinegar?
Yes, slowly, because pearl is made of calcium carbonate. In a famous story told by the Roman writer Pliny, Cleopatra won a bet with Mark Antony by dissolving a pearl from her earring in vinegar and drinking it.
Pumice
Why does pumice float?
Pumice is a holey volcanic glass that frothed up with gas and froze during an eruption; the air in its pores makes it lighter than water. That only holds while the pores are sealed and full of air: as they fill with water over time, the pumice grows heavier and sinks, and some pumice with connected pores may not float at all.
Quartz
What does quartz do in a watch?
When a quartz crystal is squeezed, it produces an electric charge; this is called piezoelectricity. Quartz watches keep time with a tiny quartz crystal that vibrates 32,768 times a second. The same property is used for frequency control in phones and computers; today this is mostly done with quartz crystals grown in laboratories.
Ruby
Why do the most famous rubies come from Myanmar?
The chromium that makes ruby red also makes it glow (fluorescence), so the ultraviolet in daylight makes the red look even more vivid. Iron suppresses this glow. The rubies of Mogok in Myanmar formed in marble, made from limestone, and contain little iron, so they are famous for their vivid red glow. The trade term “pigeon’s blood” for the finest reds is linked with these stones.
Silver
Why does silver tarnish? Is tarnished silver fake?
Silver reacts with sulfur compounds in the air and in sweat, and over time it is covered by a grey, brown or black tarnish. Tarnish is a sign of silver’s own chemistry, not of a fake. On the contrary, a piece of jewellery that never tarnishes may be rhodium-plated or an alloy that is not silver.
Spodumene
Where does the lithium in phone and car batteries come from?
Today lithium is used mostly in rechargeable batteries; the USGS estimates that about 88% of the world’s lithium use goes into batteries. Spodumene is an important source of this lithium: ore mined from the coarse-grained rocks called pegmatites is crushed, separated and turned into lithium compounds.
Sulfur
Does sulfur smell of rotten eggs?
No, pure sulfur has no smell. The rotten-egg smell at hot springs and volcanoes comes from hydrogen sulfide gas, and the sharp, choking smell of burning sulfur comes from sulfur dioxide.
Wolframite
What is the thin wire in old light bulbs made of?
Tungsten. Wolframite is one of the main ores of tungsten. Tungsten is used for light-bulb filaments, as well as for electrodes and heating elements. Its largest use today, though, is in cutting tools: according to the USGS, about 60% of the tungsten consumed in the United States goes into cemented carbide parts that resist cutting and wear.