Fact-checked by Grok 2 weeks ago

Pyrophyllite

Pyrophyllite is a soft, hydrous aluminum silicate mineral belonging to the phyllosilicate group, with the chemical formula Al₂Si₄O₁₀(OH)₂, characterized by its layered structure composed of tetrahedral silica sheets and octahedral alumina sheets that result in perfect cleavage parallel to the basal plane.^[1] It typically occurs in two habits: foliated, crystalline masses resembling mica or compact, fine-grained forms, and exhibits a pearly to dull luster, white to pale colors, a Mohs hardness of 1–2, and a specific gravity of 2.65–2.9.^[1] The name derives from the Greek words for "fire" and "leaf," reflecting its tendency to exfoliate or swell dramatically when heated due to the release of interlayer water.^[1] Pyrophyllite forms primarily through hydrothermal alteration of aluminum-rich rocks or in low-grade metamorphic environments, such as schistose deposits and veins, and is found in significant quantities in regions like North Carolina, USA, where it has been mined commercially.^[1]^[2] Its physical and chemical properties, including chemical inertness, low thermal conductivity, and high whiteness, make it valuable in industrial applications, though production has declined overall since the late 20th century due to shifts in manufacturing technologies.^[2] Key uses include as a refractory material in high-temperature ceramics and foundry molds (accounting for over 50% of U.S. sales historically), a filler and extender in paints, rubber, and paper, and in the production of electrical insulators and ceramic tiles.^[2] Emerging applications include thermal energy storage materials derived from low-grade ores.^[3] As of 2019, global production was approximately 922,000 metric tons, with the United States a major producer; more recent data (as of 2023) indicate U.S. output fluctuations, with an estimated decrease in 2023 following an increase in 2022.^[2]^[4]

Etymology and History

Etymology

The name pyrophyllite is derived from the Greek words pyr (πῦρ), meaning "fire," and phyllon (φύλλον), meaning "leaf," in reference to the mineral's characteristic exfoliation or delamination into leafy structures when subjected to heat.^[1] This etymology highlights the observable behavior where the mineral swells and separates along its layers, resembling leaves expanding in fire.^[5] The term first appeared in English between 1820 and 1830, borrowed from the German Pyrophyllit, which similarly stems from the same Greek roots.^[6] Early mineralogical descriptions noted this "fire-leaf" property, particularly the swelling of certain varieties to many times their original volume when heated before a blowpipe, a diagnostic test that contributed to its naming.^[5]

Discovery and Early Recognition

Pyrophyllite was formally recognized as a distinct mineral species in the early 19th century, with its initial scientific description provided by German chemist Rudolf Hermann in 1829. Hermann identified the mineral during studies in the Ural Mountains of Russia, where it occurred in quartz veins associated with gold deposits, and published his analysis of its chemical decomposition in the Annalen der Physik und Chemie. The name "pyrophyllite" was coined by Hermann from the Greek words pyr (fire) and phyllon (leaf), alluding to the mineral's characteristic exfoliation into thin, leaf-like sheets when heated.^[7] Early European observations of pyrophyllite focused on its presence in metamorphic rocks, distinguishing it from similar phyllosilicates like talc through its hardness and thermal behavior. By the mid-19th century, it was documented in prominent mineralogical texts, such as James Dwight Dana's A System of Mineralogy (first edition 1837, with subsequent editions expanding on its properties and occurrences). These descriptions solidified pyrophyllite's place in mineral classification systems, emphasizing its role as an aluminum-rich phyllosilicate formed under low-grade metamorphic conditions. In the United States, the first significant deposits of pyrophyllite were identified in North Carolina's Carolina Slate Belt during the late 19th century, with initial recognition around 1856 in Moore County. This discovery spurred early commercial interest, as the mineral's fine-grained, white varieties proved suitable for grinding into powder; production of pyrophyllite-based crayons began around 1880, marking the onset of industrial exploitation. By the early 20th century, a dedicated processing plant was established near Robbins in 1921 to support growing demand in ceramics and other applications.^[8] Pyrophyllite's role in early geological surveys became prominent in the 1920s, particularly through investigations by the North Carolina Geological Survey. A comprehensive report by J.L. Stuckey in 1928 detailed the mineral's deposits across the Deep River region, mapping occurrences in the slate belt and analyzing their geological context, which informed subsequent resource assessments. These surveys highlighted pyrophyllite's abundance in metamorphic terrains and laid the groundwork for systematic study in North America.

Chemical Composition and Structure

Chemical Formula and Composition

Pyrophyllite is a hydrous aluminum silicate mineral with the chemical formula \mathrm{Al_2Si_4O_{10}(OH)_2}. This formula represents a 2:1 phyllosilicate, where two tetrahedral sheets of silica tetrahedra sandwich a central octahedral sheet. The mineral's idealized composition, expressed in oxide equivalents, consists of approximately 28.3% \mathrm{Al_2O_3}, 66.7% \mathrm{SiO_2}, and 5.0% \mathrm{H_2O} by weight, reflecting the structural incorporation of aluminum, silicon, oxygen, and hydrogen.^[9]^[10] As a dioctahedral phyllosilicate, pyrophyllite features aluminum cations occupying only two of the three available octahedral sites in the central sheet, resulting in a net layer charge of zero and distinguishing it from trioctahedral counterparts like talc. The hydroxyl groups ((\mathrm{OH})_2) within the octahedral sheet are crucial for maintaining electrostatic balance and overall structural stability, linking the aluminum octahedra and facilitating weak interlayer bonding.^[11]^[12] In natural occurrences, pyrophyllite often contains trace impurities through isomorphous substitutions, such as iron (Fe^{3+}) or magnesium (Mg^{2+}) replacing aluminum in octahedral sites. These substitutions can alter the mineral's color, shifting from pure white in high-purity forms to pale green, yellow, or brownish tones depending on iron content.^[13]^[14]

Crystal Structure and Layering

Pyrophyllite exhibits a 2:1 phyllosilicate structure, consisting of a central octahedral sheet sandwiched between two tetrahedral sheets. The octahedral sheet is gibbsite-like, composed of Al(OH)₃ units where aluminum ions occupy two-thirds of the available sites in a dioctahedral configuration, while the tetrahedral sheets are formed by linked SiO₄ tetrahedra. This arrangement results in neutral layers due to the lack of significant isomorphic substitution, with the aluminum and silicon distribution providing the compositional basis for the stable layering.^[15]^[16] The crystal symmetry of pyrophyllite is typically monoclinic in its 2M polytype or triclinic in the 1Tc form, with a space group of C1 for the latter. Unit cell parameters for the 1Tc polytype include a ≈ 5.16 Å, b ≈ 8.96 Å, and c ≈ 9.35 Å, corresponding to a basal spacing of approximately 9.2 Å, which reflects the thickness of a single 2:1 layer. The dioctahedral occupancy in the octahedral sheet—where only two out of three sites are filled by Al³⁺ ions—maintains layer neutrality in pure pyrophyllite.^[16]^[15]^[17] Interlayer bonding in pyrophyllite is dominated by weak van der Waals forces between the basal oxygen atoms of adjacent tetrahedral sheets, with distances around 3.1–3.2 Å. This minimal bonding strength accounts for the mineral's characteristic foliated cleavage and propensity for delamination, allowing layers to separate easily along the (001) plane under mechanical stress or hydration. The orthogonal nature of the ideal 2:1 layer unit cell, with C2/m symmetry, further underscores the structural integrity within layers contrasted against interlayer weakness.^[15]

Physical and Optical Properties

Appearance and Crystal Habits

Pyrophyllite typically appears in pale hues, ranging from white and gray to pale blue, pale green, pale yellow, or brownish green, with variations often resulting from impurities such as iron oxides.^[20]^[1]^[13] These colors contribute to its subtle, earthy aesthetic in both crystalline and massive forms. The mineral manifests in two primary crystal habits: crystalline folia, which form thin, leafy plates up to several centimeters across, and compact masses that present as granular, foliated, or earthy aggregates.^[20] It also occasionally develops as fine-grained laminae or spherulitic clusters of needlelike radiating crystals, enhancing its layered, platy texture.^[20] Pyrophyllite exhibits perfect basal cleavage along {001}, producing thin, flexible but inelastic sheets that display a pearly to dull luster.^[20]^[1] The sheets are opaque to translucent, imparting a soft visual depth, and the mineral has a characteristic greasy or soapy feel due to its low hardness.^[13]^[20]

Mechanical, Thermal, and Optical Characteristics

Pyrophyllite is characterized by a low hardness of 1 to 2 on the Mohs scale, which makes it exceptionally soft and prone to scratching.^[20] Its specific gravity varies between 2.65 and 2.90, reflecting the lightweight nature of this aluminum silicate mineral.^[20] The sheet-like atomic arrangement contributes to its perfect cleavage along the {001} plane and a flexible yet inelastic tenacity, often imparting a soapy or greasy feel to the mineral.^[20] In terms of thermal behavior, pyrophyllite exfoliates and swells into fan-like structures when heated. Dehydroxylation commences at approximately 500°C and extends through 900°C, marking the loss of structural water without immediate lattice collapse. The mineral maintains structural integrity and exhibits high thermal stability, enduring temperatures up to 1700°C in refractory contexts.^[21]^[22] Optically, pyrophyllite displays biaxial negative character with refractive indices of nα = 1.534–1.556, nβ = 1.586–1.589, and nγ = 1.596–1.601, and 2V(meas.) = 53°–62°.^[20] Birefringence is δ = 0.044–0.062, contributing to its subdued interference colors in thin sections.^[20] Pleochroism is weak or absent in colorless varieties but may appear faintly in those with pale green or yellowish hues due to minor absorption differences parallel to the basal plane.^[23]

Geological Occurrence

Formation Mechanisms

Pyrophyllite primarily forms through low-grade metamorphism in the greenschist facies, where aluminum-rich protoliths such as shales or aluminous sediments undergo transformation under relatively low temperatures and pressures.^[24]^[25] This process often involves the dehydration reaction of kaolinite with quartz to produce pyrophyllite, stabilizing in environments with high alumina and silica availability but limited potassium activity.^[26] Hydrothermal alteration represents another key mechanism, where pyrophyllite precipitates from silica- and alumina-rich fluids circulating through fractures in host rocks, typically under acidic conditions with pH values around 2 to 5.^[27]^[28] These fluids, often derived from magmatic or meteoric sources, interact with felsic volcanics or meta-volcanic rocks, leading to vein and fracture fillings.^[29] Secondary formation occurs via the alteration of feldspars or other silicates in schistose rocks during regional metamorphism, where hydrolytic processes replace primary minerals with pyrophyllite in aluminum-enriched zones.^[30] In metamorphic settings, pyrophyllite commonly associates with quartz, sericite, and kyanite, reflecting shared stability in aluminous, low-grade conditions.^[31] Its composition, Al₂Si₄O₁₀(OH)₂, contributes to this stability by accommodating high silica-to-alumina ratios in such environments.^[25]

Principal Deposits and Localities

China is a leading global source for pyrophyllite and talc, with combined reserves estimated at 60 million metric tons as of 2025.^[32] The United States ranks as a major producer, with significant deposits concentrated in the Carolina slate belt of North Carolina, where mining operations have been active since the late 19th century. These deposits, first systematically documented in state geological surveys around 1900, have supported consistent extraction for industrial purposes.^[33] Other important localities include India, particularly in Rajasthan, where substantial production occurs alongside deposits in Andhra Pradesh and Madhya Pradesh; Brazil's Minas Gerais region; Mexico; Switzerland; Belgium; and Australia's New South Wales.^[1] In India, output from these areas contributes significantly to regional ceramics industries, with Rajasthan hosting multiple active mines.^[34] Brazil's deposits in Minas Gerais and Bahia are key for export-oriented mining.^[1] Pyrophyllite occurs in various deposit types, including bedded forms within schists, as seen in North Carolina's Deep River region, and vein-hosted varieties associated with hydrothermal activity, such as those in Cape Breton, Canada.^[35] These vein deposits in Cape Breton are linked to epithermal systems and have potential for industrial quarrying.^[36] Global annual production of pyrophyllite was approximately 737,000 metric tons as of 2023, directed mainly toward industrial applications like refractories and fillers, with China and India together accounting for over 60% of output.^[37] Detailed mappings of U.S. deposits, including those in North Carolina, were advanced by the U.S. Geological Survey starting in the 1920s, aiding resource evaluation and development.^[31]

Industrial Applications

Ceramic and Refractory Uses

Pyrophyllite plays a key role as a flux in ceramic production, where it lowers the melting point of glazes and bodies, enabling faster firing cycles at temperatures as low as 1100°C.^[37] This fluxing action improves the workability of ceramic mixtures by enhancing plasticity and reducing viscosity during forming, while minimizing excessive shrinkage that could lead to defects.^[13] As a result, it contributes to superior mechanical properties, translucence, and crack-free glazing in products such as tiles, sanitary ware, and electrical insulators.^[13] In refractory applications, pyrophyllite's high alumina content, typically 18–21%, imparts excellent resistance to thermal shock, making it suitable for high-temperature environments.^[13] It is commonly incorporated into furnace linings and insulating bricks that can withstand service temperatures up to 1700°C, with potential stability extending to 1810°C through conversion to mullite upon heating.^[38] These properties position pyrophyllite as a partial substitute for clay grog in fireclay refractories, offering better volume stability and performance in iron and steel production.^[39] For both ceramic and refractory uses, pyrophyllite is processed by grinding into a fine powder, often to particle sizes around 44 microns, to facilitate uniform mixing with other raw materials.^[13] During firing, it undergoes dehydration between 400°C and 700°C, which expands the material and enhances porosity in the final product without disrupting the crystal lattice.^[40] Historically, pyrophyllite has been used in U.S. ceramics, particularly in North Carolina.^[41] By the late 20th century, its use had expanded globally, with ceramics and refractories accounting for over 70% of domestic consumption in the U.S. by 1996, and significant modern production in Asia driving its integration into international ceramic manufacturing.^[41]^[13]

Filler, Extender, and Other Applications

Pyrophyllite serves as an effective filler in paints and coatings due to its platy structure and high refractive index (1.534–1.601), which enhance opacity, barrier properties, and film durability while reducing cracking and improving dispersion.^[42] Its softness (Mohs hardness 1–2) and chemical inertness allow it to function as a cost-effective extender pigment, often replacing talc by lowering oil absorption and volatile organic compound emissions in formulations.^[42]^[43] In the paper industry, finely ground pyrophyllite acts as a filler to improve smoothness, printability, and overall quality, leveraging its low density and platy morphology for better sheet formation and reduced weight.^[42] Typical additions range from 10–20% in filler compositions, enhancing strength without compromising brightness or opacity.^[13] Similarly, in rubber production, it functions as a dusting agent and extender, where its lubricity and low toxicity prevent sticking during processing and boost product durability through inert reinforcement.^[42] Beyond these, pyrophyllite finds applications in cosmetics as an absorbent powder base, valued for its softness and chemical stability that ensure safe, talc-alternative formulations in products like powders and creams.^[42] In agriculture, it serves as a carrier for pesticides and fertilizers, utilizing its adsorption capacity and low density to promote even distribution, slow nutrient release, and improved soil structure.^[44] For foundry operations, its lubricity enables use as a mold release agent, facilitating easy separation and reducing defects in castings.^[45] Pyrophyllite's low toxicity and inert nature make it ideal for consumer products, minimizing health risks in direct-contact applications like cosmetics and agriculture.^[42] This environmental compatibility, combined with its role in eco-friendly fillers, supports market growth, with the global pyrophyllite sector projected to expand at a compound annual growth rate of 5.9% from 2025 to 2030, as projected in 2024, driven by demand for sustainable alternatives.^[38]^[46]

Distinct Varieties

Pyrophyllite occurs primarily in two morphological varieties: foliated and compact (or massive). The foliated variety consists of thin, flexible, leaf-like plates that form through metamorphic processes in veins and schists, often exhibiting a pearly luster due to its platy structure.^[1] This form is commonly found in aluminum-rich metamorphic rocks and is valued for its ability to be finely ground into powders suitable for high-precision applications, such as in ceramics and fillers requiring uniform particle size.^[47] In contrast, the compact or massive variety appears as dense, earthy aggregates or blocks, frequently impure with quartz or other silicates, and lacks the distinct foliation of the platy form.^[48] It develops in similar geological settings but is more suited to coarser industrial uses, including as a low-cost extender in paints and plastics where purity is less critical.^[49] A notable subtype is agalmatolite, also known as pagodite, which represents a dense, fine-grained variety prized for its soapstone-like carvability.^[50] This carving-grade material, often grayish-green or yellowish, originates from altered volcanic rocks and has been extensively used in China for intricate sculptures and ornamental objects, such as pagoda figures, due to its softness and workability.^[51] Color variations in these varieties, ranging from white to pale green or brown, arise from trace impurities like iron oxides, aiding in their identification during mining.^[1] Another recognized form is the rectorite-associated variety, characterized by interlayered structures of pyrophyllite with mica-like minerals, particularly rectorite, a regularly interstratified smectite-mica.^[52] This subtype forms in advanced hydrothermal alteration zones within shales, where pyrophyllite develops through the progressive metamorphism of precursor clays, resulting in mixed-layer clays stable under low- to medium-grade conditions.^[53] Such associations are documented in deposits like those in north-central Utah, where they contribute to the mineral's role in altered sedimentary sequences.^[52]

Comparison with Similar Minerals

Pyrophyllite shares a layered phyllosilicate structure with several related minerals, but key compositional and physical differences aid in its identification.^[54] Compared to talc, both minerals are soft and exhibit foliated habits, with Mohs hardness values of 1 for talc and 1 to 2 for pyrophyllite.^[55] However, pyrophyllite substitutes aluminum for magnesium in its structure, contrasting with talc's composition of Mg₃Si₄O₁₀(OH)₂, and lacks the distinctive soapy tactile feel characteristic of talc.^[56]^[57] Pyrophyllite also displays a slightly higher refractive index range of 1.55 to 1.60 compared to talc's 1.54 to 1.59.^[13] Diagnostic distinction via X-ray diffraction reveals a basal spacing of approximately 9.2 Å for pyrophyllite, versus 9.3 Å for talc, while infrared spectroscopy highlights differences in OH stretching modes, with pyrophyllite showing an intense band in the near-infrared region around 4000–4700 cm⁻¹ and distinct peak patterns in the 400–600 cm⁻¹ range.^[58]^[59] In contrast to sericite, a fine-grained variety of muscovite, pyrophyllite lacks interlayer potassium cations that stabilize sericite's structure.^[54] This absence contributes to pyrophyllite's greater propensity for thermal exfoliation upon dehydroxylation, where interlayer water loss leads to structural expansion, unlike the more rigid sericite framework.^[60] Relative to kaolinite, another clay-like phyllosilicate, pyrophyllite features a 2:1 layer structure with tetrahedral-octahedral-tetrahedral sheets, whereas kaolinite has a 1:1 configuration.^[61] Pyrophyllite exhibits lower plasticity in aqueous suspensions due to its neutral layers and forms under higher-temperature hydrothermal or metamorphic conditions, typically above 200°C, compared to kaolinite's prevalence in low-temperature weathering environments.^[62]^[63]

References

[1]
Pyrophyllite: Mineral information, data and localities.
Pyrophyllite ; Specific Gravity: 2.65 - 2.9 ; Crystal System: Triclinic ; Member of: Pyrophyllite-Talc Group ; Name: From the Greek for "fire" (πῦρ, pyr) and "leaf" ...
[2]
[PDF] Talc and Pyrophyllite | 2019 Minerals Yearbook
Pyrophyllite followed a similar trend to that of talc, with sales decreasing since 1979 as use in the manufacture of refractory products decreased owing to ...
[3]
Pyrophyllite - Geology Page
Jul 15, 2014 · Name Origin: From the Greek for fie and leaf, in allusion to its tendency to exfoliate into fan shapes when heated. Pyrophyllite is a ...
[4]
PYROPHYLLITE Definition & Meaning - Dictionary.com
Pyrophyllite definition: a phyllosilicate, AlSi 2 O 5 (OH), usually having a white or greenish color, and occurring in either foliated or compact masses, ...
[5]
[PDF] MINERALS OF THE MONTMORILLONITE GROUP
HERMAN, RUDOLPH. 1829, Zerlegung des Pyrophyllites: Annalen der Bhysik und. Chemie (Poggendorff), Band 15, pp. 592, 593. HEWETT, D. F.. 1917, The origin of ...
[6]
Mining | NCpedia
Used in ceramics, insecticides, and other products, pyrophyllite was first identified in 1856 in Moore County. In 1921 a processing plant was built near Robbins ...<|control11|><|separator|>
[7]
TALC AND PYROPHYLLITE - Official Publication of SME
It has the theoretical composition Al2O3.4SiO2.H2O, which equates to 28.3 percent Al2O3, 66.7 percent SiO2 and 5 percent H2O. It also occurs with other ...Missing: weight | Show results with:weight
[8]
The beneficiation of the Pütürge pyrophyllite ore by flotation
Theoretically, pyrophyllite (Al4Si8O20(OH)4) is composed of. 66.65% SiO2, 28.35% Al2O3 and 5.00% H2O, and it is a dioctahe- dral 2:1 clay mineral consisting of ...
[9]
Ab Initio Study of Sorption on Pyrophyllite: Structure and Acidity of ...
Aug 7, 2025 · Pyrophyllite, Al2[Si4O10](OH)2, is the simplest structural prototype for 2:1 dioctahedral phyllosilicates. Since it does not possess ...
[10]
MOLECULAR DYNAMICS SIMULATIONS OF PYROPHYLLITE ...
Aug 1, 2015 · Aluminum ions occupy two of three possible sites in the octahedral ... aluminum hydroxyl group is evident when the B edge surface >Al-OH ...
[11]
Pyrophyllite: An Economic Mineral for Different Industrial Applications
Pyrophyllite, when heated at different temperatures, passes through several thermal transformation phases (Table 4). One of the most critical transformations is ...Missing: blowpipe | Show results with:blowpipe
[12]
Pyrophyllite - AZoM
Jun 6, 2002 · Pyrophyllite is soft ceramic ... magnesium is substituted for aluminium. In fact, chemical; tests are often requires to tell the two apart.
[13]
Pyrophyllite - an overview | ScienceDirect Topics
Pyrophyllite (Al4Si8O20(OH)4) is the end member of dioctahedral 2:1 clay minerals containing no isomorphic substitution and therefore no layer charge. All ...
[14]
[PDF] THE CRYSTAL STRUCTURES OF PYROPHYLI,ITE, lTC ... - RRuff
For dioctahedral layer structures, it is well established (see survey by Bailey, 1966) that the Al, O(OH) dioctahedral sheets depart from the ideal arrangement ...
[15]
Structures of the 2:1 Layers of Pyrophyllite and Talc
Dec 1, 2012 · To determine the relationships between the symmetry of the overall pyrophyllite and talc structure and the symmetry of individual layers, ...
[16]
[PDF] Pyrophyllite Al2Si4O10(OH)2 - Handbook of Mineralogy
Optical Properties: Translucent to opaque. Color: White, pale blue, yellow, apple-green, grayish green, brownish green; in thin section, colorless.
[17]
Pyrophyllite lost foam casting coating and preparation method thereof
Pyrophyllite has fine texture, Mohs hardness 1.5-2.0, density 2.65-2.90g/cm 3 , and refractoriness >1700°C. Pyrophyllite has many characteristics such as ...
[18]
Pyrophyllite Value, Price, and Jewelry Information
Aug 6, 2018 · Vague shadow edge on refractometer at about 1.6. Refractive Index. 1.534-1.601. Specific Gravity. 2.65-2.90. Stone Sizes. Cabochons and carvings ...
[19]
Pyrophyllite Al4[Si8O20](OH)4 - GeoScienceWorld
Pleochroism. Absorption greater for vibration directions in (001) plane. Unit cell a ~ 5.17 A˚ , b ~ 8.96 A˚ , or a ~ 5.16 A˚ , b ~ 8.96 A˚ , c ~ 18.68 A˚ , b ...
[20]
Pyrophyllite - WGNHS
Pyrophyllite is a micaceous mineral formed as a result of the relatively low grade metamorphism of aluminum-rich rocks. It can also form as a hydrothermal ...Missing: mechanisms | Show results with:mechanisms
[21]
Microstructures and interlayering in pyrophyllite from the Coastal ...
Mar 2, 2017 · Pyrophyllite, once thought rare, is a low-grade metamorphic mineral typically formed in Al-rich rocks, such as highly aluminous metapelites ...
[22]
Metamorphic Reactions - Tulane University
Mar 21, 2011 · In low grade metamorphic in this system, the reaction: Al2Si4O10(OH)2 <=> Al2SiO5 + 3SiO2 + H2O Pyrophyllite Ky or Andal Qtz fluid. defines a ...
[23]
[PDF] GEOLOGY OF THE CARPENTIER PYROPHYLLITE DEPOSIT
Jan 24, 1979 · Pyrophyllite is a soft light coloured mineral, white greyish or greenish, similar in appearance and properties to talc, although harder than ...
[24]
Genesis of the Baiyun pyrophyllite deposit in the central Taihang ...
The pyrophyllite ores primarily occur as subparallel-sheeted veins in fractures of the late Archean meta-volcanic rocks, and locally as filling fractures within ...
[25]
[PDF] Pyrophyllite and metamorphism in the Carolina slate belt
Exploitable pyrophyllite at Hillsborough, North Carolina, occurs in late Precambrian metavolcanics of the Carolina slate belt as vein and fracture fillings ...Missing: first identification
[26]
10.5: Clay Minerals - Geosciences LibreTexts
Jun 3, 2025 · The important point here is that while kaolin, pyrophyllite and Illite are typically derived from alteration of minerals like feldspar and ...
[27]
[PDF] Pyrophyllite, and kyanite and related minerals in the United States ...
Introduction. The important deposits of pyrophyllite, and of kyanite and the related minerals (sillimanite, andalu- site, dumortierite, and topaz) in the ...
[28]
[PDF] TALC AND PYROPHYLLITE1 - USGS.gov
One company in North Carolina mined and processed pyrophyllite in 2021. Domestic production data were withheld to avoid disclosing company proprietary data and ...
[29]
Talc and pyrophyllite deposits in North Carolina
Talc and pyrophyllite deposits in North Carolina ; Date: 1900 ; Creator: ["Pratt, Joseph Hyde, 1870-1942."] ; Place: ["North Carolina, United States"] ; Series ...
[30]
[PDF] Indian Minerals Yearbook 2018
Production of pyrophyllite is mainly reported from Chhatarpur,. Tikamgarh and Shivpuri districts of Madhya. Pradesh; Mahoba, Hamirpur, Jhansi and Lalitpur.Missing: Kerala | Show results with:Kerala
[31]
Pyrophyllite from Coxheath Cu-Mo-Au deposit, Cape Breton Co ...
Pyrophyllite from. Coxheath Cu-Mo-Au deposit, Cape Breton Co., Nova Scotia, Canada ; Locality type: Deposit ; Species: Pyrophyllite ; Formula: Al 2Si 4O 10(OH) ; Al ...
[32]
Pyrophyllite Occurrences in the Coxheath area, Cape Breton Island
Coxheath area contains significant pyrophyllite deposits, important for industrial mineral applications. · Pyrophyllite's chemical composition averages 70.83% ...
[33]
Pyrophyllite Market Analysis | Industry Growth, Size & Forecast Report
Sep 29, 2025 · India alone produced roughly 150,000 tons, equal to 24-25% of global output, conferring raw-material security to regional ceramics clusters.
[34]
Pyrophyllite Refractories: Transactions of the Indian Ceramic Society
Jul 11, 2014 · It was observed that raw pyrophyllite could favourably replace clay grog by 30 to 60% in fireclay refractories with better volume stability on ...Missing: sources | Show results with:sources
[35]
SOME PYROCHEMICAL PROPERTIES OF PYROPHYLLITE * - 1938
Pyrophyllite lost its water of constitution between 400° and 700°C without any heat effect or breakdown of the crystal lattice. There was, however, an increased ...
[36]
[PDF] TALC AND PYROPHYLLITE - Amazon AWS
The Department of Defense authorized the disposal of 974 metric tons of block and lump talc and 988 tons of ground talc from the National Defense Stockpile.
[37]
https://www.mordorintelligence.com/industry-reports/pyrophyllite-market
[38]
[PDF] Structural, Thermal, and Novel Functional Applications of ... - IJNRD
Refractive Index 1.534–1.601 ... Due to its platy morphology and chemical inertness, it is used as a functional filler in paints, plastics, and rubber.
[39]
Pyrophyllite Market Size And Share | Industry Report, 2030
The global pyrophyllite market size was valued at USD 73.9 million in 2024 and is projected to grow at a CAGR of 5.9% from 2025 to 2030.
[40]
Pyrophyllite Market Unlocking Growth Opportunities: Analysis and ...
Rating 4.8 (1,980) Jan 19, 2025 · Pyrophyllite can be used as an alternative to kaolin in various sectors such as fiberglass, plastics, pulp and paper, agriculture, ceramics, ...<|control11|><|separator|>
[41]
Pyrophyllite mineral - Digitalfire
Many other minerals can be found associated with it (e.g. kyanite, andalusite, topaz, quartz, sericite, chlorotoid, pyrite, chlorite, feldspar, hematite, ...
[42]
Pyrophyllite Dust – Its Effects And Control - OneMine.org
PYROPHYLLITE is a hydrous aluminum silicate (A12Si4O10(OH)2)1 that ... The foliated variety resembles talc in that it has a greasy feel, a pearly ...
[43]
Talc and Pyrophyllite Statistics and Information - USGS.gov
Statistics and information on the worldwide supply of, demand for, and flow of the mineral commodities talc and pyrophyllite.Missing: 1920s | Show results with:1920s
[44]
Agalmatolite - CAMEO
Apr 24, 2022 · Agalmatolite is a variety of Pyrophyllite. It has a specific gravity of 2.8-2.9 and has been used as a substitute for Talc. Synonyms and ...
[45]
Agalmatolite gemstone information - Gemdat.org
Agalmatolite. An old 19th century name for a carving stone originally from China. A dense form of one or more of pinite, pyrophyllite and/or talc.<|separator|>
[46]
[PDF] The Origin of Pyrophyllite - Rectorite in Shales of North Central Utah
Differential thermal analysis curves of pyrophyllite samples from Utah ... He stated that swelling takes place via the py- rophyllite-like uncharged ...Missing: blowpipe | Show results with:blowpipe
[47]
The Origin of Pyrophyllite Rectorite in Shales of North Central Utah
Jul 1, 2024 · Pyrophyllite subsequently formed from the alteration of rectorite during advancing metamorphism and is the stable end member of the clay mineral ...
[48]
Basics of Clay Minerals and Their Characteristic Properties
Vermiculite clays are weathered micas where the potassium ions are replaced by magnesium and iron ions between the molecular sheets [9, 37]. Non-expanding clay ...
[49]
Talc and Pyrophyllite - ScienceViews.com
The name pyrophyllite comes from the Greek words pyr meaning fire and phyllon meaning leaf, a reference to the fact that it flakes when heated. The name was ...Missing: German first English<|control11|><|separator|>
[50]
PYROPHYLLITE - H.K. Microns
Pyrophyllite is a phyllosilicate mineral species belonging to the clay family and composed of aluminium silicate hydroxide: AlSi 2 O 5 OH.Missing: etymology | Show results with:etymology
[51]
[PDF] CHAPTER 1 MINERALOGY OF TALC - VTechWorks
Talc is a very versatile mineral used in many industrial applications due to mainly its unique surface chemistry and lamellar crystal habit.
[52]
The beneficiation of the Pütürge pyrophyllite ore by flotation
Sep 26, 2022 · Samples from the pyrophyllite reserves in the Malatya–Pütürge region, used in the production of the whitest cement in Europe, were beneficiated using flotation.
[53]
(PDF) Near-Infrared Spectroscopy Study of OH Stretching Modes in ...
Dec 2, 2022 · Fourier transform infrared spectroscopy was used to differentiate between pyrophyllite and talc. In the 400–600 cm−1 region, pyrophyllite ...
[54]
Thermal Reactions of Pyrophyllite Studied by High-Resolution Solid ...
Aug 9, 2025 · At elevated temperatures and 1 atm, pyrophyllite undergoes a dehydration reaction forming pyrophyllite dehydroxylate (Al2S&0, 1), which ...
[55]
Clay mineral - Kaolin, Serpentine, Group | Britannica
Pyrophyllite-talc group Minerals of this group have the simplest form of the 2:1 layer with a unit thickness of approximately 9.2 to 9.6 Å—i.e., the structure ...
[56]
Weathering & Clay Minerals - Tulane University
Nov 18, 2014 · Thus, they form by alteration of minerals like muscovite and feldspar. Illite clays are the main constituent of ancient mudrocks and shales ...
[57]
3. Formation and alteration of clay materials - GeoScienceWorld
Kaolinite is concentrated in humid tropical latitudes where it is derived from kaolinite-rich soils formed under the intense chemical weathering regime via ...<|separator|>