Field Notes
Field Notes and Market Intelligence
Notes from the buying trips and the laboratory literature. Written from Bangkok, between flights.
The Stones
Aquamarine: Properties, Origins, Treatments and Value
Emerald's clean-living relative: the same beryl, coloured by iron instead of chromium, growing in large flawless crystals that make it abundant, affordable, and rarely serious.
Tanzanite: Properties, Origin, Treatment and Value
A blue-violet zoisite from a single deposit in northern Tanzania, found in 1967, named by Tiffany, and heated almost without exception. A stone whose entire story fits on one hill.
Garnet: The Family, Properties, Origins and Value
Not one stone but six end members and every mixture between them, in every colour but blue, almost never treated, and priced from ornamental to serious in the space of a single word.
Spessartite Garnet: Properties, Origins and Value
The garnet that is orange by nature rather than by accident. Manganese colours it, iron reddens it, and nothing on earth treats it.
Tsavorite: Properties, Origins, Treatments and Value
A green garnet fifty years old in the trade, born in one metamorphic belt, untreated because nothing improves it, and rare above five carats because the rock will not give it up whole.
Spinel: Properties, Origins, Treatments and Value
The stone in the Black Prince's Ruby. Cubic, singly refractive, almost never treated, and priced for most of its history as something it was not.
Star Sapphire and Star Ruby: Asterism Explained
Corundum that grew with three sets of needles at sixty degrees, cut so the needles throw a star. The stones the trade paid for before it learned to want transparency.
Grandidierite: Properties, Origins, Rarity and Value
Named for a French explorer, found in southern Madagascar in 1902, and for a century known only as an opaque mineral. Then a pocket of transparent crystals turned it into one of the rarest gems anyone can buy.
Paraíba Tourmaline: Properties, Origins, Treatments and Value
Copper in a tourmaline, discovered in a hill in Brazil after years of digging, and now the most expensive tourmaline on earth by a distance. The name is a colour, an origin, and an argument.
Tourmaline: Properties, Varieties, Origins and Value
A boron silicate so chemically tolerant that it will take almost any element and turn it into a colour. One family, every hue, and one variety that outprices the rest by a multiple.
Alexandrite: Properties, Origins, Treatments and Value
Chrysoberyl with chromium in exactly the wrong place, so the same stone is green by a window and red by a candle. The rarest of the great stones by any honest count.
Diamond: Properties, Grading, Treatments and Value
Pure carbon, the hardest natural substance, and the most systematically graded object in the trade. What the system measures, and what it cannot.
Emerald: Properties, Origins, Treatments and Value
Green beryl, born fissured, coloured by two elements that should never have met beryllium. The stone the trade has been oiling for as long as there has been a trade.
Sapphire: Properties, Origins, Treatments and Value
Corundum in every colour except red. Blue is the one the world means, and blue is a conversation between two impurities that were not supposed to meet.
Ruby: Properties, Origins, Treatments and Value
Red corundum, coloured by an awkward guest in its lattice. Everything the trade does around ruby follows from how rarely that guest arrives in quantity.
Unheated Burmese Ruby
Mogok ruby glows because the marble it grew in held almost no iron. Most of what the trade says about Burmese ruby follows from that, or ought to.
Ceylon Sapphire
The overwhelming majority of blue sapphire in the market has been in a furnace. Heat is legitimate when it is disclosed, and it is the reason unheated Ceylon is priced apart from everything around it.
Padparadscha Sapphire
Sapphire’s most contested name covers a mixture of pink and orange that no two laboratories bound the same way in practice. Buyers lose money on that disagreement.
Colombian Emerald
Muzo, Chivor and Coscuez, and the one treatment I accept. The oil scale runs from none to significant. I stop at minor, and I make that call from the report.
Spinel
Some of the most famous rubies in history were never rubies. Spinel is singly refractive and almost never treated, and the trade still prices it as though it were standing in for something better.
Tsavorite
A green garnet coloured by vanadium and chromium, out of Kenya and Merelani. Almost nothing is done to it, and almost none of it comes out large. Those two facts set the price.
Global Sourcing Expeditions
Zambian Emerald: Kafubu and the Case for the Other Green
The Copperbelt supplies a large share of the world's emerald and almost none of its legend. For some buyers that is exactly the point.
Madagascar Sapphire: Ilakaka and the Modern Market
A sandstone plain in the south-west of Madagascar produced one of the largest sapphire rushes in history. What it left behind is a market worth understanding.
Cobalt Blue Spinel from Luc Yen, Vietnam
A marble valley in northern Vietnam produces the rarest blue in the trade, in sizes that make a two-carat stone a serious object.
Mogok, Burma: Buying Ruby at the Source
A valley of marble in upper Burma has produced the world's reference ruby for centuries. Buying there is a discipline of light, patience and paper.
Buying Gemstones in Bangkok: How the Trade Really Works
Nearly every fine coloured stone on earth passes through this city. So does nearly every treated one. Notes from the office towers of Silom.
How a Gem Hunter Works: Private Gemstone Sourcing Explained
The title sounds romantic. The work is a sequence of decisions, most of them refusals. Here is the sequence, in the order it actually happens.
Kashmir Sapphire: Why Origin Sets the Price
A deposit worked out in a decade still sets the ceiling for blue sapphire. The velvet explained, and the proof the paper must carry.
Who Is Lambert Vissot: The Gem Hunter
Who the hunter is, and how I run a mandate.
Mahenge, After the Rush
Eighteen years since the great spinel find. What the hills produce now, and what the first wave got wrong.
Technical Gemmology
Glass-Filled Ruby and Other Traps for the Unwary Buyer
Every fraud in this trade is a true word attached to the wrong stone. The stone is rarely the problem; the label is.
Hue, Tone, Saturation: How Gemstone Colour Is Graded
Colour is not one thing. It is three measurements and one trick of the cut, and the price of a stone lives in the second measurement.
Native Cut, Windows, and the Cost of Recutting
Rough is priced by weight, so it is cut to keep weight. Nearly everything wrong with a native cut follows from that.
How to Read a Gem Lab Report
Five laboratories, five house styles, one stone. What the paper states, and the order in which to read it.
Pigeon’s Blood: What the Term Certifies
Two words that move six figures. What the laboratories mean by them, and what they leave out.
Reading a Ruby in Poor Light
Back rooms have bad lamps for a reason. Notes on judging color when the seller controls the light.
Investment Advisory
Where to Buy Fine Gemstones: Dealer, Auction, or Jeweller
The same stone can be bought in three rooms at three prices with three kinds of risk. Knowing which room you are in is most of the skill.
Record Ruby, Sapphire and Emerald Prices, Explained
The record books are not a price list. They are a record of what happens when size, colour, paper and two determined bidders meet in one room.
Building a Coloured Gemstone Collection: A Ten-Year Plan
A collection is not a drawer of pretty things. It is a sequence of decisions taken over years, and the first one decides most of the others.
Gemstone Due Diligence: Provenance, Paperwork, Escrow
At the top of the market the stone is the smaller risk. The paper, the seller and the sequence of payment are where money is actually lost.
How to Commission a Bespoke Gemstone Search
A search is only as good as its brief. The mandates that find stones share a shape, and the ones that never close share a different one.
Are Coloured Gemstones an Investment?
What a stone does, and does not do, as an asset.
Price Per Carat: Why Size Multiplies Value
A five-carat stone is not five one-carat stones. Where the curve bends, and why weight is the wrong thing to buy.
Burmese or Mozambique: What Origin Does to a Ruby
Mozambique produces much of the fine ruby on the market. Burma still sets the price. The difference is iron.
What Unheated Means, and What It Costs
The word carries a premium of thirty to fifty percent. Where that premium comes from, and when it is worth paying.
The next note follows the next trip.