Pyroxene vs. Amphibole — What's the Difference?
Edited by Tayyaba Rehman — By Fiza Rafique — Updated on October 1, 2023
Pyroxene and Amphibole are both mineral groups in igneous and metamorphic rocks; Pyroxene has a simpler structure and shorter prismatic crystals, while Amphibole has a more complex structure and longer prismatic crystals.
Difference Between Pyroxene and Amphibole
Table of Contents
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Key Differences
Pyroxene and Amphibole are two distinct mineral groups found primarily in igneous and metamorphic rocks. They play pivotal roles in the classification and identification of these rocks. Pyroxene minerals typically exhibit a short prismatic crystal habit, and they have an orthorhombic or monoclinic crystal system. In contrast, Amphibole minerals are characterized by their long prismatic crystal habit and belong exclusively to the monoclinic crystal system.
Both Pyroxene and Amphibole are double-chain silicates; however, their internal structures are notably different. Pyroxene has a simpler single-chain structure where silicate tetrahedra share two oxygens. Amphibole, on the other hand, boasts a double-chain structure where the tetrahedra share two or three oxygens, making it more complex.
Chemically, Pyroxene and Amphibole show variations. Pyroxenes typically consist of calcium, magnesium, and iron silicates. Their composition allows them to be an essential component in mafic igneous rocks like basalt and gabbro. Conversely, Amphiboles have a broader range of chemical compositions, with the inclusion of elements like aluminum, sodium, and potassium, and they are often found in both mafic and felsic igneous rocks.
In terms of their appearance in hand samples, Pyroxene and Amphibole can sometimes be challenging to distinguish due to their dark colors. Pyroxenes usually display square or eight-sided cross-sections, while Amphiboles often show a more elongated and rectangular cross-section.
Another distinction between Pyroxene and Amphibole lies in their cleavage. Pyroxenes exhibit two cleavages at nearly 90 degrees, making them easily identifiable under a microscope. Amphiboles, however, possess two cleavages that intersect at roughly 60 and 120 degrees, giving them a more angular appearance.
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Comparison Chart
Crystal Structure
Single-chain silicate
Double-chain silicate
Crystal Habit
Short prismatic
Long prismatic
Chemical Composition
Calcium, magnesium, iron silicates
Broader range including aluminum, sodium, potassium
Cleavage
Two cleavages at nearly 90 degrees
Two cleavages at roughly 60 and 120 degrees
Common Appearance
Square or eight-sided cross-sections
Elongated, rectangular cross-sections
Compare with Definitions
Pyroxene
A group of dark-colored minerals found in igneous rocks.
The basalt rock contained a significant amount of Pyroxene.
Amphibole
A group of dark-colored minerals found in various igneous rocks.
The granite sample showed traces of Amphibole.
Pyroxene
A single-chain silicate mineral with a simple structure.
Pyroxene's distinctive cleavage patterns aid geologists in its identification.
Amphibole
A double-chain silicate mineral with a complex structure.
Amphibole's intricate structure makes it unique among rock-forming minerals.
Pyroxene
A mineral with two cleavages at nearly 90 degrees.
Under the microscope, Pyroxene's cleavage is easily distinguishable.
Amphibole
A mineral with diverse chemical compositions, including elements like aluminum and sodium.
The Amphibole's composition made it versatile in various rock types.
Pyroxene
A short prismatic mineral of orthorhombic or monoclinic crystal system.
Pyroxene's short prismatic structure is a key characteristic geologists note.
Amphibole
A mineral with two cleavages at roughly 60 and 120 degrees.
Amphibole's angular cleavage is a distinguishing feature.
Pyroxene
A mineral primarily composed of calcium, magnesium, and iron silicates.
The presence of Pyroxene gives the rock its dark hue.
Amphibole
A long prismatic mineral of the monoclinic crystal system.
The elongated shape of Amphibole crystals is notable in rock samples.
Pyroxene
The pyroxenes (commonly abbreviated to Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula XY(Si,Al)2O6, where X represents calcium (Ca), sodium (Na), iron (Fe II) or magnesium (Mg) and more rarely zinc, manganese or lithium, and Y represents ions of smaller size, such as chromium (Cr), aluminium (Al), iron (Fe III), magnesium (Mg), cobalt (Co), manganese (Mn), scandium (Sc), titanium (Ti), vanadium (V) or even iron (Fe II).
Amphibole
Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain SiO4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown.
Pyroxene
Any of a group of crystalline silicate minerals common in igneous and metamorphic rocks and containing two metallic oxides, as of magnesium, iron, calcium, sodium, or aluminum.
Amphibole
Any of a large group of structurally similar silicate minerals, such as hornblende, that have a crystalline structure consisting of a double chain of linked SiO4 units and that contain various combinations of sodium, calcium, magnesium, iron, and aluminum. Several varieties of asbestos are fibrous forms of amphiboles.
Pyroxene
(mineral) Any of a group of crystalline minerals containing silicates of iron, magnesium and calcium.
Amphibole
(mineral) Any of a large group of structurally similar hydrated double silicate minerals, containing various combinations of sodium, calcium, magnesium, iron, and aluminium/aluminum
Pyroxene
A common mineral occurring in monoclinic crystals, with a prismatic angle of nearly 90°, and also in massive forms which are often laminated. It varies in color from white to dark green and black, and includes many varieties differing in color and composition, as diopside, malacolite, salite, coccolite, augite, etc. They are all silicates of lime and magnesia with sometimes alumina and iron. Pyroxene is an essential constituent of many rocks, especially basic igneous rocks, as basalt, gabbro, etc.
Amphibole
A common mineral embracing many varieties varying in color and in composition. It occurs in monoclinic crystals; also massive, generally with fibrous or columnar structure. The color varies from white to gray, green, brown, and black. It is a silicate of magnesium and calcium, with usually aluminium and iron. Some common varieties are tremolite, actinolite, asbestus, edenite, hornblende (the last name being also used as a general term for the whole species). Amphibole is a constituent of many crystalline rocks, as syenite, diorite, most varieties of trachyte, etc. See Hornblende.
Pyroxene
Any of a group of crystalline silicate mineral common in igneous and metamorphic rocks
Amphibole
A mineral or mineral variety belonging to the amphibole group
Common Curiosities
Which mineral has cleavages at nearly 90 degrees?
Pyroxene exhibits two cleavages at nearly 90 degrees.
Are Pyroxene and Amphibole similar minerals?
They are both dark-colored minerals found in igneous rocks but have different structures and compositions.
Are both Pyroxene and Amphibole found in the same type of rocks?
Both can be found in igneous rocks, but their presence varies based on the rock's specific composition.
Which mineral group, Pyroxene or Amphibole, has a broader chemical composition?
Amphibole has a broader chemical composition compared to Pyroxene.
Is Pyroxene exclusively found in mafic rocks?
While common in mafic rocks like basalt, Pyroxene can also be present in other rock types.
Which has a simpler structure, Pyroxene or Amphibole?
Pyroxene has a simpler single-chain structure compared to Amphibole's double-chain.
How can I distinguish Pyroxene from Amphibole in hand samples?
Pyroxene typically has square or eight-sided cross-sections, while Amphibole has elongated, rectangular ones.
Are the cleavage angles of Pyroxene and Amphibole similar?
No, Pyroxene has cleavages at nearly 90 degrees, while Amphibole's are at roughly 60 and 120 degrees.
Do both Pyroxene and Amphibole belong to the same crystal system?
Pyroxene can be orthorhombic or monoclinic, while Amphibole is strictly monoclinic.
What elements are commonly found in Amphibole?
Amphibole includes elements like aluminum, sodium, and potassium.
Can both Pyroxene and Amphibole be found in metamorphic rocks?
Yes, both can be present in certain metamorphic rocks.
Which mineral, Pyroxene or Amphibole, is more elongated in form?
Amphibole is typically more elongated than Pyroxene.
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Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
