Gems
4
Friends
Sections
Corundum
Beryl
Quartz
Diamond
The Drawer
Mines
Named Stones
Cutting
Archive
36 pieces · 8 sections
Archive
Every page on the site, filed under the mineral or the section it belongs to.
Corundum
Ruby and Sapphire Are One Mineral, and the Trade Knows It
Explains how ruby and sapphire are chemically identical corundum, distinguished only by trace elements — chromium for red, iron and titanium for blue.
Colour Is Chemistry, Shape Is the Lattice
A close look at how chromium ions substitute for aluminium in the corundum crystal lattice to produce red fluorescence, and why the same mechanism in different concentrations produces pink rather than red.
Six Lines from a Single Point
Explains the optical mechanism of asterism — needle-like rutile inclusions oriented along three crystal axes reflecting light as a six-rayed star — using the Star of India and the Delong Star Ruby as documented examples.
Mogok Sits in Marble, and That Is Why Its Rubies Glow
Documents the geology of the Mogok valley in Burma — crystalline marble host rock, low iron content, high chromium — and how it produces the fluorescent red that Mogok rough is known for.
Beryl
Emerald Is the One Gemstone the Trade Agreed to Forgive
Examines how the GIA's grading system treats emerald inclusions — the jardin — differently from those in ruby or sapphire, and why a flawless emerald is treated with suspicion rather than admiration.
Muzo and Chivor Were Being Worked Before the Spanish Arrived
Documents the pre-Columbian Muisca extraction at Muzo and Chivor in Colombia's Boyacá department, tracing the mines from indigenous use through Spanish seizure to the modern concession system.
The Beryls That Are Not Emerald
Covers aquamarine (iron-blue) and morganite (manganese-pink) as beryl varieties with their own deposit records — Brazil's Minas Gerais for aquamarine, Madagascar and California for morganite — and notes where each sits in the GIA classification.
The Urals Were the Only European Source, and They Still Are
Traces the discovery of emerald-bearing mica schist near Yekaterinburg in 1831 and the subsequent Malysheva mine operation, covering the geological conditions — chromium from serpentinite intruding into beryl-bearing pegmatite — and how Ural material compares to Colombian in the record.
Quartz
Purple Quartz, and Why Heat Turns It Yellow
Explains how iron impurities and natural irradiation produce colour centres in quartz to create amethyst, and why the same material heated to 400–500°C converts to citrine — the mechanism behind much of the commercial citrine on the market.
Agate Bands Form Over Thousands of Years in a Cavity
Documents the silica-gel infiltration theory of agate banding — successive layers of chalcedony deposited in volcanic vesicles — and covers the major agate deposits at Idar-Oberstein in Germany, where the cutting and polishing tradition is documented from the 15th century.
Most Citrine in the Trade Was Amethyst Last Week
A factual account of how heat treatment transforms amethyst to citrine and smoky quartz to golden material, covering GIA's disclosure requirements and the spectroscopic markers laboratories use to distinguish natural citrine from treated material.
Diamond
Four Letters the GIA Fixed in 1953
Traces the development of the GIA's cut-colour-clarity-carat system from Robert Shipley's earlier grading work to the 1953 standardisation, covering what each grade measures and why the system was adopted industry-wide rather than remaining a single laboratory's convention.
What the Kimberley Process Actually Certifies
Documents the 2003 Kimberley Process Certification Scheme — its scope (rough diamonds only, conflict-financing definition), its membership structure and the documented criticisms of its coverage gap.
Argyle Closed in 2020 and the Pink Supply Closed with It
Documents the Rio Tinto Argyle mine in the East Kimberley region of Western Australia — its 1983 opening, its role as the source of more than 90 percent of the world's pink diamonds (per Rio Tinto figures), and its November 2020 closure after the underground ore body was exhausted.
Same Carbon, Different History
Explains the two laboratory production methods — HPHT and CVD — and the spectroscopic and inclusion-pattern markers that gemmological laboratories use to distinguish lab-grown from natural diamonds.
Auguste Verneuil Grew a Ruby in a Flame in 1902
Documents Auguste Verneuil's flame-fusion process — aluminium oxide powder, hydrogen-oxygen flame, boule formation — and its 1902 publication, covering how synthetic corundum entered the watch-bearing and gem trade and how modern laboratories identify Verneuil material by curved growth striations.
The Drawer
Spinel Borrowed Ruby's Colour, Mine, and Name
Uses the Black Prince's Ruby — identified as spinel by mineralogists in 1783 — as the entry point for explaining how spinel was systematically misidentified as ruby or sapphire for centuries, covering the chemistry difference (MgAl₂O₄ versus Al₂O₃) and the Balas ruby category in historical trade.
Coober Pedy Produces White Opal; Lightning Ridge Produces Black, and the Difference Is the Dirt
Contrasts the geology of Coober Pedy (Cretaceous sandstone, white potch) and Lightning Ridge (dark Cretaceous clay, black potch) in New South Wales to explain why the host material controls opal body colour.
Jade Is Two Minerals, and the Trade Still Uses One Name
Documents the 1863 mineralogical separation of jade into jadeite (pyroxene, Burma) and nephrite (amphibole, New Zealand, Siberia, British Columbia), covering the physical tests that distinguish them and how Chinese imperial use — documented in the Palace Museum record — predates the chemical distinction.
The Blue That Came from One Valley for Six Thousand Years
Documents the Sar-e-Sang workings in the Kokcha valley, Badakhshan — the documented source of lapis lazuli from at least 4000 BCE through Egyptian, Mesopotamian and Renaissance use (ultramarine pigment) — covering the lazurite-calcite-pyrite mineralogy and the current mine operation.
One Mineral, Every Colour in the Spectrum
Explains tourmaline's boron-silicate crystal structure and the range of substituting elements — iron, manganese, copper, lithium — that produce its colour range, from indicolite to rubellite to Paraíba copper-blue.
Mines
The Big Hole Was Dug by Hand in Twenty-Three Years
Documents the Kimberley open-cast mine — 240 metres deep, 17 hectares, dug between 1871 and 1914 largely by hand tools — covering the kimberlite pipe geology, the IDB (illicit diamond buying) legal history and the 1889 De Beers Consolidated acquisition.
Ratnapura's Gems Come Out of a Riverbed, Not a Rock Face
Documents the illam alluvial gravel deposits of the Ratnapura district in Sri Lanka's Sabaragamuwa province — the geological process by which corundum, spinel, chrysoberyl and garnet concentrate in Miocene-age river gravels — and the pit-and-winch extraction method still in use.
Ilakaka Had No Name on the Map in 1998
Documents the 1998 alluvial sapphire discovery near Ilakaka in Madagascar's Horombe Plateau — from a single roadside find to a shanty town of forty thousand within two years — covering the gem-quality range (blue, yellow, padparadscha) and the subsequent formalisation of the concession system.
Diavik and Ekati Put Canada on the Diamond Map in the 1990s
Documents the 1991 kimberlite discoveries at Lac de Gras in the Northwest Territories by Chuck Fipke and Stewart Blusson, the opening of Ekati in 1998 and Diavik in 2003, and the winter ice-road logistics that supply both operations across frozen Lac de Gras.
Named Stones
The Hope Diamond Came to the Smithsonian by Registered Post
Documents the Hope Diamond's 1958 transfer — Harry Winston's registered-mail parcel to the Smithsonian Institution's National Gem Collection — covering the stone's verified chain of ownership from Tavernier's 1666 purchase through the French Blue, the Hope family acquisition and the McLean period.
Recut in 1852, and It Lost Forty-Two Per Cent of Itself
Documents the Koh-i-Noor's 1851 display at the Great Exhibition — where its lacklustre appearance prompted Prince Albert to commission a recutting — and the 1852 Amsterdam recutting by Garrard under supervision, which reduced it from 186 carats to 105.6 carats (per the Tower of London record).
Joseph Asscher Struck the Cullinan Once and the Blade Broke
Documents the 1905 Cullinan discovery at the Premier Mine in Transvaal (3,106 carats, per the mine operator's record), the 1907 purchase by the Transvaal government and gift to Edward VII, and the January 1908 cleaving by Joseph Asscher in Amsterdam — the first blade broke on contact; the second produced nine principal stones.
The Black Prince's Ruby Has Not Been a Ruby Since 1783
Documents the spectroscopic identification of the Black Prince's Ruby as spinel by mineralogists in 1783 and its continuous display in the Imperial State Crown since 1838, covering its documented history from the 14th-century Moorish treasury forward.
The Star of India Went Out Through an Unlocked Window in 1964
Documents the October 1964 theft of the Star of India (563.35 carats, per the American Museum of Natural History) and twenty-three other gems from the J.P.
The Logan Sapphire Is the Size of an Egg and Came from Ratnapura
Documents the Logan Sapphire — 422.99 carats, cushion-cut, Sri Lanka origin, donated to the Smithsonian by Rebecca Pollard Logan in 1960 (per Smithsonian catalogue) — covering the stone's physical dimensions, its position in the National Gem Collection and the Ratnapura deposit geology that produced it.
Cutting
Three Numbers from 1919 That Nobody Has Managed to Improve On
Documents Marcel Tolkowsky's 1919 doctoral thesis at the University of London — the mathematical derivation of crown angle, pavilion angle and table percentage for maximum brilliance and fire — and how those proportions became the standard against which the GIA's cut grade is still measured.
The Rose Cut Came Before Anyone Could Do the Arithmetic
Traces the rose cut — flat base, domed crown, triangular facets — from its 16th-century appearance in Antwerp through the old mine cut (cushion outline, high crown, small table) of the 18th and 19th centuries, arguing that each cut reflects the limits of the lap and lighting technology of its period.
Why Some Stones Are Never Faceted
Explains the optical reasons cabochon cutting is used for opal (play-of-colour is a surface phenomenon destroyed by facets), star stones (asterism requires a dome to concentrate the reflection) and cat's-eye chrysoberyl.
Antwerp Cut Diamonds for Five Centuries; Surat Cut Most of Them
Documents the parallel histories of Antwerp as the dominant diamond-cutting centre from the 15th century and Surat (and the broader Gujarat industry) as the centre that came to process the majority of the world's rough by volume from the 1970s forward, covering the factory scale, the polishing-wheel technology and the GIA grading integration.
Friedrich Mohs Published His Scale in 1812 and It Measures One Thing
Documents Friedrich Mohs's 1812 publication — the ten-mineral scratch-resistance series from talc to diamond — explaining precisely what relative scratch resistance means and what it does not: it is not absolute hardness, not cleavage resistance, not toughness.