Gem library
Garnet
A whole family, from blood red to emerald green
Garnet is not a stone but a family of six main species that mix freely, covering every colour except true blue. From the blood red of almandine to the emerald green of tsavorite, prices range from €5 to €5,000 per carat.
- Hardness (Mohs)
- 6.5 – 7.5
- Density
- 3.58 – 4.32
- Crystal system
- Cubic
- Refractive index
- 1.714 – 1.895
- Cleavage
- None
Mineralogical identity
- Family
- Silicates — garnet group
- Species
- Almandine, pyrope, spessartine, grossular, andradite, uvarovite
- Variety
- Rhodolite, tsavorite, demantoid, hessonite, mandarin
- Chemical formula
- X₃Y₂(SiO₄)₃ — X = Mg, Fe, Mn, Ca; Y = Al, Fe, Cr
- Crystal system
- Cubic
- Classification
- Semi-precious stone
- Rarity
- Uncommon
- Indicative price
- €5 – 150/ct (up to €5,000/ct for demantoid and tsavorite)
Etymology
From the Latin granatum, the pomegranate: red crystals set in rock evoked the fruit's seeds.
Physical & optical properties
- Hardness (Mohs)
- 6.5 – 7.5
- Density
- 3.58 – 4.32
- Refractive index
- 1.714 – 1.895
- Birefringence
- None (isotropic)
- Cleavage
- None
- Fracture
- Conchoidal to splintery
- Lustre
- Vitreous to subadamantine
- Diaphaneity
- Transparent to opaque
- UV fluorescence
- None
- Pleochroism
- None
- Colours
- red, orange, green, brown, pink, purple
Formation, geology & history
One family, six poles
Garnets share a single cubic architecture but allow almost unlimited chemical substitution. Six species define the poles: almandine (iron-aluminium, dark red), pyrope (magnesium-aluminium, bright red), spessartine (manganese-aluminium, orange), grossular (calcium-aluminium, green to colourless), andradite (calcium-iron, green to black) and uvarovite (calcium-chromium, vivid green, rarely gem). Every blend between those poles exists: rhodolite is a pinkish-violet pyrope-almandine, tsavorite a grossular with chromium and vanadium, demantoid a chromium andradite whose lustre and fire exceed those of diamond. A gemmologist identifies the species by density and refractive index, both highly variable.
The very valuable garnets
Two varieties reach the summit. Demantoid, discovered in the Urals in 1868, has a refractive index of 1.89 and dispersion higher than diamond's: its green fire is unique. The finest Russian specimens contain fibrous chrysotile inclusions in a «horsetail» pattern, the deposit's signature, and exceed €5,000/ct. Tsavorite, a green grossular found in Kenya in 1967, rivals emerald in saturation without its fragility: harder, cleavage-free, more brilliant — it is simply unobtainable above two carats. Namibian mandarin spessartine, an incandescent orange, completes this trio of collector garnets.
History and jewellery
Bohemian garnets, tiny fiery red pyropes set in tight pavé, made the fortune of Czech workshops in the nineteenth century: Victorian parures are covered in them. The Romans already cut intaglios in almandine, and Merovingian and Visigothic goldsmiths practised garnet cloisonné — thin red plates set into gold cells, a technique visible on the Sutton Hoo treasure. Today garnet is valued for its hardness (6.5 to 7.5), total absence of cleavage and lustre: it is one of the most robust stones in daily wear.
How to recognise it
- No birefringenceCubic and therefore isotropic: between crossed polarisers garnet stays dark. Ruby, red spinel and glass behave differently (except spinel, also isotropic).
- High density3.6 to 4.3 depending on species: markedly heavier than quartz. In heavy liquid a garnet sinks where a tourmaline floats.
- Bright lustre with no cleavageFacet edges stay crisp even on antique stones, for want of cleavage. A red stone chipped along its edges is more likely topaz or fluorite.
Imitations, treatments & confusions
- Red glass («synthetic garnet»)Round bubbles, a softer lustre, lower density, blunted facets. Very common in antique costume jewellery.
- Confusion with ruby and spinelHistorically massive: most pre-nineteenth-century crown «rubies» are garnets or spinels. Garnet is darker and less fluorescent under UV.
- Garnet doublets and YAGYAG (yttrium aluminium garnet) is a laboratory synthetic used as a diamond simulant. It has nothing to do with natural garnets despite the name.
Deposits & origins
Almandine: India, Sri Lanka, Madagascar · Rhodolite: Tanzania, Mozambique · Mandarin spessartine: Namibia, Nigeria · Tsavorite: Kenya, Tanzania · Demantoid: Russia (Urals), Namibia, Madagascar · Hessonite: Sri Lanka · Historic Bohemian almandine: Czechia
Care & precautions
- Warm soapy water and a soft brush: garnet is robust and cleavage-free.
- Ultrasonic-safe except for heavily included or fractured stones.
- Avoid sudden thermal shock, especially on demantoid and included garnets.
- Prolonged salt and strong acids should be avoided; pool water poses no notable problem.
Traditions & crystal healing
- Chakras
- Root · sacral
- Zodiac signs
- Aries · Scorpio · Capricorn
- Element
- Fire
- Month
- January
A stone of vitality and commitment in tradition: it is said to support physical energy, perseverance and the courage to see things through. Crusaders wore it against wounds, and medieval tradition credited it with stopping haemorrhage — an analogical reasoning based on its colour.
The virtues described here belong to tradition and cultural heritage. They are in no way medical advice and never replace a consultation.
Frequently asked questions
Is garnet always red?
No, that is a stubborn myth. The family covers orange (spessartine), green (tsavorite, demantoid), pink (rhodolite), brown (hessonite) and colourless (grossular). Only true blue is almost entirely absent.
Garnet or ruby?
Ruby is harder (9), fluoresces red under UV and shows birefringence. Garnet is isotropic, darker, non-fluorescent, and generally worth ten to a hundred times less.
Is garnet suitable for an everyday ring?
Yes, very much so: hardness 6.5-7.5 with no cleavage at all, which makes it more impact-resistant than topaz or emerald, though those are harder.