History
Bertrandite carries the name of a man who never dug it out of the ground. It honours the French mineralogist Émile Bertrand (1844–1909), and the story of how it got that name is a small relay of credit.
The mineral first turned up near Nantes, in western France. Bertrand made an early analysis of the new material in 1880. The chemist Alexis Damour then completed the full description, and in 1883 named the species after him.
Bertrand was no minor figure. He helped found the Société française de minéralogie et de cristallographie, the country's main mineral-science society. His name still lives on a piece of laboratory glass too — the Bertrand lens, an optical part used to study crystals under the microscope.
Industrial & practical applications
More than 90 percent of the world's beryllium — the lightweight metal prized for stiff, dimensionally stable parts — is won from bertrandite ore. That makes this modest white mineral the metal's single most important source.
Almost all of it comes from one place. The Spor Mountain deposit in Utah is the sole working source of beryllium in the United States, mined and processed by a single company.
The metal that bertrandite yields is hard to substitute. Beryllium metal goes mainly into aerospace and defence parts, chosen for its stiffness, light weight, and dimensional stability — its tendency to hold its exact shape across a wide temperature range.
Alloyed with copper, it does a different job. Beryllium-copper alloys carry high electrical and thermal conductivity along with strength, hardness, and good corrosion and fatigue resistance, and they are nonmagnetic. That mix is wanted in springs, electrical connectors, and non-sparking tools.
Supply is narrow. The United States is one of only three countries that process beryllium ores into finished beryllium products, and it supplies most of the rest of the world. Apparent US consumption in 2024 came to about 170 tons.
Working the ore demands care. Inhaling airborne beryllium dust can cause chronic beryllium disease, a serious long-term lung disease, and prolonged exposure causes lung cancer in humans — the metal is classed as a Group 1 carcinogen, meaning it is known to cause cancer in people.
Where it forms, where it's found
- Geological setting
In pegmatite.
Granite fissures or miarolitic cavities, pegmatites, greisen. Alteration product of beryl, rarely primary mineral.
- Type locality
- Petit-Port
- Nantes
- Nantes
- Loire-Atlantique
- Pays de la Loire
- France
47.2430°, -1.5566°
Safety & handling
Physical
Optical
- Optical type
- Biaxial (-) · 2V measured = 73 – 81° · 2V calc = 76°
- Refractive index
- 1.591 – 1.614
- Surface relief
- Moderate
- Principal indices
- nα 1.591 · nβ 1.605 · nγ 1.614
- Dispersion
- r < v weak
Crystallography
- Space group
- #21
- Cell parameters
- a = 8.7135(4) Å · b = 15.268(1) Å · c = 4.5683(3) Å
- Ratio a:b:c
- 1 : 1.752 : 0.524
- Z
- 4
- Morphology
Thin tabular, prismatic to needle-like.
- Twinning
Common on (011), (021); heart- or V-shaped twins.
Chemical composition
- Impurities
- Al
- Fe
- Ca
Synonyms
- Hessenbergit
- Hessenbergite
In other languages
- French
- bertrandite
- German
- Bertrandit
- Spanish
- Bertrandita
- Italian
- Bertrandite
- Portuguese
- bertrandita
- Japanese
- ベルトラン石
- Chinese
- 矽鈹石 · 羟硅铍石
- Russian
- Бертрандит
- Arabic
- بيرترانديت
Classification
9.BD.05
- 9SilicatesClass
- 9.BSorosilicatesDivision
- 9.BDSi2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordinationGroup
- 9.BD.05BertranditeSpecies
56.01.01.01
- 56Sorosilicates Si2o7 Groups, with Additional O, Oh, F and H2oClass
- 56.01Si2O7 Groups and O, OH, F, and H2O with cations in [4] coordinationType
- 56.01.01— unnamed intermediate level —Group
- 56.01.01.01BertranditeSpecies
14.3.2
- 14Silicates not Containing AluminumClass
- 14.3Silicates of BeGroup
- 14.3.2BertranditeSpecies
Literature, links & citation
- 1880Bertrand, Émile (1880) Nouveau minéral des environs de Nantes. Bulletin de Minéralogie, 3 (4). 96-100 doi:10.3406/bulmi.1880.1566DOI: 10.3406/bulmi.1880.1566
- 1882Des Cloizeaux (1882) Note sur la probabilité de l'existence à Barbin, près Nantes, du nouveau silicate d'alumine, fer et chaux de Petit-Port décrit par M. Bertrand en 1880. Bulletin de la Societe Mineralogique de France: 5: 176.
- 1883Bertrand, Emile (1883) Nouveau minéral des environs de Nantes [bertrandite]. Bulletin de Minéralogie, 6 (8) 248-252 doi:10.3406/bulmi.1883.1823DOI: 10.3406/bulmi.1883.1823
- 1883Damour, Augustin-Alexis (1883) Note et analyse sur le nouveau minéral des environs de Nantes. Bulletin de Minéralogie, 6 (8). 252-254 doi:10.3406/bulmi.1883.1824DOI: 10.3406/bulmi.1883.1824
- 1888Scharizer, R. (1888) Der Bertrandit von Pisek. Zeitschrift für Kristallographie, 14 (1). 33-42 doi:10.1524/zkri.1888.14.1.33DOI: 10.1524/zkri.1888.14.1.33
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Bertrandite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/bertrandite-642},
note = {Accessed 2026-05-11}
}