What does amphibole mean?
Amphibole is the name of a large and chemically complex group of rock-forming silicate minerals characterized by a double-chain crystal structure. Common members include hornblende, actinolite, and tremolite, and amphiboles are major constituents of many igneous and metamorphic rocks, such as granite, diorite, schist, and gneiss. Geologists identify them by their elongated prismatic crystals and their distinctive cleavage angles of roughly 56 and 124 degrees. The term also carries a darker modern meaning: certain fibrous forms, known as amphibole asbestos, were widely used in insulation and construction before being linked to serious respiratory diseases, making the word familiar in public-health and remediation contexts. Derived from the Greek 'amphibolos', meaning ambiguous or doubtful — a nod to the minerals' bewildering variability — amphibole remains primarily a scientific term, encountered in textbooks, laboratory reports, and environmental assessments rather than everyday conversation.
nounAny of a large group of dark, prismatic silicate minerals forming double-chain crystal structures, common in igneous and metamorphic rocks such as hornblende, actinolite, and tremolite.
- Any of a group of rock-forming double-chain silicate minerals, including hornblende, actinolite, and tremolite.
- Specifically, amphibole asbestos — fibrous forms of these minerals once used industrially and now recognized as serious health hazards.
"The thin section revealed long prismatic crystals of amphibole cutting across the quartz grains."
"Under the microscope, the amphibole crystals showed their characteristic two cleavage planes meeting at angles of about 56 and 124 degrees."
"Old insulation containing amphibole asbestos was carefully removed from the building by licensed contractors."
The plural is standard when referring to multiple specimens, varieties, or members of the amphibole group.
"Amphiboles are among the most chemically diverse groups of rock-forming minerals."
The word 'amphibole' comes from the Greek for 'ambiguous' — fittingly, since these minerals were so variable in form that early mineralogists couldn't pin them down.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of amphibole
The word amphibole was coined by the French mineralogist René Just Haüy around the turn of the nineteenth century, drawing on the Greek 'amphibolos', meaning 'ambiguous' or 'doubtful'. Haüy chose the name because these minerals occur in such varied forms and compositions that early mineralogists found them difficult to classify with certainty. The Greek root, related to 'amphi-' meaning 'on both sides' or 'around', also gives us words like amphibian and amphitheater, though those senses are unrelated to the mineral itself.
How amphibole is actually used
A technical term used chiefly in geology, mineralogy, and materials science; rarely encountered outside scientific or industrial contexts. In health-and-safety discussions, 'amphibole' often specifically denotes the hazardous fibrous (asbestiform) varieties, as opposed to serpentine asbestos.
Easily confused with amphibole
An amphibian is a cold-blooded vertebrate such as a frog or salamander, whereas an amphibole is a silicate mineral; the words share a Greek root but refer to entirely different things.
Pyroxenes are single-chain silicates structurally similar to amphiboles, which are distinguished by their double-chain structure and the presence of hydroxyl groups.