What is Phyllite – All You Need to Know About This Rock

What is Phyllite – All You Need to Know About This Rock

Mar 28, 2023

The team at World of Stones USA has explained about many different types of rocks in the past. Today, by continuing the series, we are going to share all aspects of Phyllite rocks in a nutshell from a commercial point of view rather than the academic one.

What is Phyllite?

Phyllite is a metamorphic rock with crinkled or wavy foliation. The word Phyllite originates from the Greek word “Phyllion,” which means leaf. 

Now, we know what Phyllite is.  The next question arises: How is it formed in nature?

What is the protolith or parent rock type of Phyllite?

Shale, pelite, or slate are protolith or parents of phyllite rocks. So, like slate, Phyllite has a typical texture called “Phyllitic sheen” and has fissility or tendency to split into sheets like slate rocks.

What is the prime difference between phyllite and slate rocks from a geological point of view?

According to Wikipedia

Slate has extremely fine Clay flakes in a preferred orientation.

Phyllite has fine-grained Mica flakes in a preferred orientation.

Schist has large flakes in a preferred orientation.

It means Phyllite is in between the gradation of a degree of metamorphism of slate to schist. 

How Does Phyllite Form?

When Slate rocks’ further metamorphism occurs, and very fine-grained Mica attains perfect orientation, the Phyllite forms.

  • Slate rocks have clay minerals in semi-random orientation. 
  • When slate rocks are buried further and gain high pressure,
  • The extremely fine clay flacks turn into Mica, and the flacks of clay minerals gain parallel alignment. 
  • Heat and chemical reactions turn clay mineral grains into chlorite or mica minerals. They are enlarged versions of fine-grained clay flakes. 
  • Thus, they form phyllite rocks.
  • Of course, further metamorphism and sedimentation process turn Phyllite into Schist, and then Geiss by enlarging mica flakes.

What are colors found in Phyllite?

  • Phyllite is used to find in black to shiny gray and greenish-gray colors, which are in lighter shades and tones compared to slate rocks.
  • Often phyllite weathers into tan or brown color over time.
  • The reflective sheen of Phyllite usually gives a silvery or non-metallic appearance.


What is the mineral composition of Phyllite?

Scielo.br has given the mineralogical composition of phyllites by the Rietveld Method. 


Content (%)






Muscovite 1M






Muscovite 2M1













According to the table above, we can say:

  • Phyllite has tiny gains of mica minerals such as Muscovite or sericite.
  • Phyllite contains almost half the amount of quartz in its constitution.
  • Quartz and feldspar were found abundantly in Phyllite.
  • Crystals of andalusite, cordierite, biotite, staurolite, and garnet are found in Phyllite.
  • Porphyroblasts or large crystals are found in parallel orientation in Phyllite.
  • Organic minerals transform into graphite and give phyllite black to dark gray shades that adorn it a submetallic luster.
  • Phyllite is a soft and brittle rock with a 1 to 2 Mohs hardness scale.
  • It has a specific gravity of 2.72-3.
  • Phyllite is resistant to heat, cold, and water, so it is the right candidate for outdoor applications.

What is the use of Phyllite or applications of Phyllite in the construction industry?

It is excellent as crushed stones used in constructing buildings, as the base material for paths, driveways, and roads. It is often used in landscaping, paving like patios and decks. We can use Phyllite wherever we can apply slate stones.

Shily appearance and a higher amount of quartz render the Phyllite a decorative stone. It can beautify your interior and exterior spaces like a façade when used smartly.

In landscaping, you can use phyllite aggregates as stunning elements in décor.

Where is Phyllite found?

Phyllite occurs across the world in many regions, such as:

  • The Appalachians in North America
  • Scottish Highlands 
  • The Alps in Europe


World of Stones USA in Maryland has a big inventory of phyllite pavers to use in outdoor patio making in various surface textures to make it anti-skid.

You will have the best prices for the best and desired quality of phyllite stones at World of Stones USA.



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