What it is confused with
Green glass, tsavorite garnet, green tourmaline, doublets and synthetic emeralds. Synthetic stones are often too clean; natural emeralds almost always show inclusions.
Green to bluish green
Emerald birthstone
Emerald, the birthstone for May, is beryllium aluminum silicate (Be₃Al₂Si₆O₁₈) colored by chromium or vanadium, green to bluish green, rated 7.5–8 on the Mohs scale. Traditionally, it is linked to loyalty, growth and honest speech — attributed, not demonstrated.
- Mohs hardness
- 7.5–8 scratches window glass
- Crystal system
- Hexagonal Be₃Al₂Si₆O₁₈
- Pliny, AD 77
- Book 37.16 as “smaragdus”
- Main sources today
- Colombia also Zambia, Brazil
Pliny, Natural History, tr. Bostock and Riley.
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Properties
Composition
Beryllium aluminum silicate (Be₃Al₂Si₆O₁₈) colored by chromium or vanadium
Hardness (Mohs)
7.5–8
Crystal system
Hexagonal
Color
Green to bluish green
Mined in
Colombia, Zambia, Brazil, Ethiopia, Afghanistan
Worth knowing
Almost every emerald contains internal fractures — the trade calls them jardin, "garden". A flawless emerald is more suspicious than impressive.
History
Mined in Egypt from the late Ptolemaic period, around the first century BCE; Cleopatra is said to have claimed the mines.
Buying
Buying Emerald: fakes, value and treatments
What decides the price
Color outweighs everything else, with vivid, slightly bluish green valued most. Filling fractures with oil or resin is nearly universal, and the amount of filling changes the price.
Where it is used
The step-cut "emerald cut" was developed to reduce stress on this brittle stone while showing its color.
A less familiar fact
The Mogul Emerald, carved with Shia prayers and dated 1695, weighs about 218 carats.
Practical
Caring for Emerald
How to clean it
Warm soapy water and nothing else. Never ultrasonic — nearly all emeralds are oil-treated to fill fractures, and ultrasound drives the oil out.
How to tell it is real
A flawless emerald should raise suspicion rather than excitement: genuine stones nearly always show internal fractures the trade calls jardin. Perfectly clean green stones are usually glass or synthetic.
How hard is Emerald?
Emerald is harder than quartz yet fragile. Nearly every stone has fractures filled with oil, and a knock, heat or an ultrasonic cleaner can open them, so it is best kept in a protective setting. Only Aquamarine shares its place on our scale. Among the stones in this reference, the next softer is Tourmaline (7–7.5) and the next harder Spinel (8).
Emerald, at 7.5–8, is harder than 35 of the other 42 stones here and softer than 6.
Primary source
What Pliny the Elder wrote about Emerald
“Indeed there is no stone, the colour of which is more delightful to the eye; for whereas the sight fixes itself with avidity upon the green grass and the foliage of the trees, we have all the more pleasure in looking upon the smaragdus, there being no green in existence of a more intense colour than this.”
“The Emperor Nero used to view the combats of the gladiators upon a smaragdus.”
Pliny the Elder, The Natural History, translated by John Bostock and H. T. Riley (London: H. G. Bohn, 1855–57), book 37, chapter 16 — read the original text.
Pliny’s smaragdus covered several green stones, but its most prized kinds are generally identified with emerald. The sentence before the one about Nero says that a flat smaragdus reflects images like a mirror, so Nero may have used his as a mirror rather than as a lens. Who Pliny was and why we quote him →
Traditional associations
Emerald is traditionally linked to loyalty, growth and honest speech. Chakra in crystal practice: Heart. Element: Earth.
Questions about Emerald
What is Emerald made of?
Beryllium aluminum silicate (Be₃Al₂Si₆O₁₈) colored by chromium or vanadium, crystallizing in the hexagonal system.
Which month is Emerald the birthstone for?
May.
Where does Emerald come from?
Colombia, Zambia, Brazil, Ethiopia, Afghanistan.
Can Emerald be worn every day?
With care. At 7.5–8 on the Mohs scale it can be worn often, but watch out for knocks, heat and ultrasonic cleaners, which open its oiled fractures.
Sources
Statements of fact on this page were checked against these sources in October 2026. How we choose and check sources: editorial policy.
Cite this page
AstroHot. “Emerald Birthstone: The May Stone — Meaning and Properties.” Accessed October 28, 2026. https://astrohot.com/crystals/gemstones/emerald/
For Wikipedia
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