elements
Diamond
C
- Crystal system
- cubic
- Hardness
- 10 on the Mohs scale
- Lustre
- adamantine
- Colour
- Colourless, and also yellow, brown, blue, pink, green, black
- Where it forms
- At depths of 150 kilometres or more, over a billion years or more, and brought up rapidly in kimberlite eruptions. Diamond is metastable at the surface: it is slowly turning into graphite, at a rate that will outlast the sun.
- Chiefly from
- BotswanaRussiaDemocratic Republic of the CongoCanadaSouth Africa
Why it is that colour
Pure diamond is colourless. Nitrogen gives yellow, boron gives blue, and the pinks and reds come from structural distortion rather than any impurity — which is why they are so rare and so poorly understood.
Safety
Chemically inert and safe. Diamond dust is an abrasive, not a poison.
Where it comes from
The Kimberley Process was established in 2003 to keep conflict diamonds out of the trade, and its adequacy is widely disputed — it defines conflict diamonds narrowly, as those financing rebel movements against legitimate governments, which excludes state violence and labour abuse. Botswana’s industry is generally regarded as well governed; other producers less so. Laboratory-grown diamonds are chemically identical, cost a fraction, and now take a meaningful share of the market.
Historical use
India was the world’s only significant source until Brazilian discoveries in the 1720s and South African ones in the 1860s. The South African finds transformed diamond from genuinely rare to merely controlled, and the control — through De Beers, from 1888 — is what kept the price up for a century.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Ancient in India, where diamonds were known and traded from at least the fourth century BC and appear in Sanskrit texts with associations of invincibility — the Greek adamas, unconquerable, gives the English word. Its status as the standard engagement stone is not ancient at all: it dates from a De Beers advertising campaign begun in 1938, which coined "A Diamond Is Forever" in 1947.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
The diamond engagement ring is the most successful piece of marketing in the history of gemstones, and its history is unusually well documented. Diamond sales were falling in the 1930s. De Beers hired N. W. Ayer in 1938, and the campaign that followed established the diamond ring as the expected token of engagement, promoted the idea that a man should spend a fixed proportion of his salary on one, and produced the line "A Diamond Is Forever" in 1947. The proportion was not traditional; it was invented, and revised upward over time.
The line is also a piece of supply management. A diamond that is never resold never competes with a new one, and a stone framed as a permanent symbol is a stone that does not come back to market.
Meanwhile the mineral itself is genuinely extraordinary — the hardest natural substance, the best thermal conductor known, formed under conditions that exist only deep in the mantle, and older than almost anything else you can hold.
Identity checked against IMA-CNMNC master list, June 2025.