Month: November 2025

Amazonite

Amazonite is a green variety of microcline feldspar (KAlSi₃O₈), prized both as a gemstone and for its striking color.

🌍 Origins and Naming

  • Name Origin: Named after the Amazon River, though no deposits are actually found there. The name reflects its vivid green color reminiscent of tropical landscapes.
  • Mineral Group: Feldspar (alkali feldspar, specifically microcline).
  • Discovery: Known since antiquity; used in jewelry and ornamental objects.

🔬 Chemical and Structural Properties

  • Formula: KAlSi₃O₈ (microcline feldspar).
  • Crystal System: Triclinic.
  • Color: Bright green to bluish-green, sometimes mottled with white.
  • Cause of Color: Trace amounts of lead and water in the feldspar lattice, plus possible iron content.
  • Habit: Blocky crystals, massive aggregates.
  • Hardness: ~6–6.5 on Mohs scale.
  • Specific Gravity: ~2.56–2.58.
  • Cleavage: Perfect in two directions, typical of feldspars.
  • Luster: Vitreous.

⚙️ Geological Occurrence

  • Found in granitic pegmatites, often associated with quartz, albite, and smoky quartz.
  • Localities:
    • Colorado, USA (classic locality, especially Pikes Peak region).
    • Brazil.
    • Madagascar.
    • Russia (Ural Mountains).
    • Namibia.

📖 Scientific and Collector Significance

  • Gemstone Use: Cut into cabochons, beads, and ornamental carvings. Rarely faceted due to cleavage.
  • Collectors: Valued for its vivid green color and association with pegmatite minerals.
  • Industrial Note: No major industrial use; significance lies in gemology and mineral collecting.

✨ Conclusion

Amazonite is a green variety of microcline feldspar, treasured for its vivid color and ornamental use. Found in pegmatites worldwide, it bridges mineralogical interest and gemstone appeal.

In short: Amazonite = green microcline feldspar, triclinic, gemstone from pegmatites, famous in Colorado and worldwide.

 

Amatrice

Amatrice is an obsolete mineral name that was historically applied to a variety of scapolite. It is not recognized today as a distinct mineral species by the International Mineralogical Association (IMA).

🌍 Origins and Naming

  • Name Origin: From Amatrice, a town in Lazio, Italy, where the mineral variety was first described.
  • Status: Discredited; modern mineralogy treats “amatrice” as a synonym for scapolite rather than a separate species.
  • Historical Context: In the 19th century, local or compositional variants of scapolite were often given distinct names before structural and chemical analysis clarified their identity.

🔬 Chemical and Structural Properties (Scapolite Group)

  • General Formula: (Na,Ca)₄(Si,Al)₁₂O₂₄
  • Mineral Group: Feldspathoid group (scapolite series: marialite ↔ meionite).
  • Crystal System: Tetragonal.
  • Color: White, gray, pink, violet, or yellow depending on impurities.
  • Habit: Prismatic crystals, granular aggregates, massive forms.
  • Hardness: ~5–6 on Mohs scale.
  • Specific Gravity: ~2.6–2.8.
  • Luster: Vitreous.

⚙️ Geological Occurrence

  • Environment: Found in metamorphic rocks (marbles, gneisses) and some igneous rocks.
  • Associated Minerals: Calcite, diopside, feldspar, quartz.
  • Localities: Amatrice (Italy), and scapolite-bearing rocks worldwide.

📖 Scientific and Collector Significance

  • Petrology: Scapolite minerals are important indicators of metamorphism and metasomatism.
  • Collectors: Crystals can be attractive, especially violet scapolite varieties, though “amatrice” as a name is obsolete.
  • Industrial Uses: Scapolite has limited industrial use; occasionally cut as a gemstone.

✨ Conclusion

Amatrice is an obsolete synonym for scapolite, first described from Amatrice, Italy. While the name is no longer valid, it reflects the historical tendency to assign local variants distinct names before mineral classification was standardized.

In short: Amatrice = old name for scapolite, tetragonal feldspathoid, first described in Amatrice, Italy.

 

Amargosite

Amargosite is an obsolete mineral name, historically used as a synonym for bentonite (a clay composed mainly of montmorillonite). It is not recognized today as a distinct mineral species by the International Mineralogical Association (IMA).

🌍 Origins and Naming

  • Name Origin: Derived from the Amargosa region in Nevada, USA, where bentonite deposits occur.
  • Status: Considered a synonym of bentonite rather than a valid mineral species.
  • Historical Context: In older mineralogical references, “amargosite” was used to describe clay-rich bentonite deposits, but modern classification subsumes it under bentonite.

🔬 Chemical and Structural Properties (Bentonite / Montmorillonite)

  • Formula: (Na,Ca)₀.₃₃(Al,Mg)₂Si₄O₁₀(OH)₂·nH₂O (generalized for montmorillonite).
  • Mineral Group: Smectite clays.
  • Crystal System: Monoclinic (but crystals are extremely small, often cryptocrystalline).
  • Color: White, cream, gray, or pale green.
  • Habit: Earthy, clay-like masses.
  • Hardness: ~1–2 on Mohs scale.
  • Specific Gravity: ~2.3–2.6.
  • Special Property: High swelling capacity and cation-exchange ability due to its layered structure.

⚙️ Geological Occurrence

  • Formation: Alteration of volcanic ash in sedimentary basins.
  • Localities: Amargosa region (Nevada, USA), Wyoming, and worldwide bentonite deposits.
  • Associated Minerals: Zeolites, feldspars, volcanic glass.

📖 Scientific and Industrial Significance

  • Petrology: Important indicator of volcanic ash alteration.
  • Industrial Uses (Bentonite):
    • Drilling muds in oil and gas exploration.
    • Foundry sands (binding agent).
    • Absorbents (cat litter, spill control).
    • Sealants for landfills and ponds.
    • Food and pharmaceutical uses (clarifying agents, detox clays).
  • Collectors: Not collected as a mineral specimen; valued for industrial utility.

✨ Conclusion

Amargosite is simply an obsolete synonym for bentonite, a clay dominated by montmorillonite. While the name survives in historical references, modern mineralogy recognizes only bentonite as the correct term.

In short: Amargosite = old name for bentonite (montmorillonite-rich clay), not a valid mineral species today.

Sources: Mindat – Amargosite entry

Amarantite

Amarantite is a rare hydrated iron sulfate mineral with the formula Fe³⁺₂(SO₄)O·7H₂O. It is one of the more unusual secondary sulfates formed in oxidized environments, notable for its striking reddish coloration.

🌍 Origins and Naming

  • Name Origin: From the Greek amarantos (“unfading”), referring to its persistent reddish color.
  • Discovery: First described in 1850.
  • Type Locality: Copiapó, Atacama Desert, Chile.

🔬 Chemical and Structural Properties

  • Formula: Fe³⁺₂(SO₄)O·7H₂O
  • Mineral Group: Sulfates.
  • Crystal System: Monoclinic.
  • Color: Bright red to reddish-brown.
  • Habit: Acicular (needle-like) crystals, fibrous aggregates, crusts.
  • Hardness: ~2 on Mohs scale (very soft).
  • Specific Gravity: ~2.1–2.2 (light due to hydration).
  • Luster: Vitreous to silky.
  • Streak: Pale yellow to orange.

⚙️ Geological Occurrence

  • Formation: Secondary mineral formed in the oxidation zones of pyrite and other iron sulfides.
  • Environment: Found in arid climates where evaporation concentrates sulfate-rich solutions.
  • Associated Minerals: Copiapite, coquimbite, halotrichite, melanterite, and other hydrated iron sulfates.
  • Localities:
    • Copiapó, Chile (classic locality).
    • Other occurrences in arid mining districts worldwide.

📖 Scientific and Collector Significance

  • Petrology: Indicator of highly oxidized, sulfate-rich environments.
  • Collectors: Attractive red acicular crystals are prized, though delicate and unstable.
  • Industrial Note: No commercial use; valued mainly for rarity and mineralogical interest.

✨ Conclusion

Amarantite is a rare red hydrated iron sulfate, first described from Chile. It forms delicate acicular crystals in oxidized sulfide deposits, serving as a vivid indicator of sulfate-rich environments but remaining a collector’s curiosity rather than an economic resource.

In short: Amarantite = Fe³⁺₂(SO₄)O·7H₂O, red hydrated iron sulfate, monoclinic, first found in Copiapó, Chile.

 

Alvite

Alvite is an obsolete mineral name that was historically applied to a variety of albite (NaAlSi₃O₈), the sodium-rich endmember of the plagioclase feldspar series. It is not recognized today as a distinct species by the International Mineralogical Association (IMA).

🌍 Origins and Naming

  • Name Origin: “Alvite” was used in older mineralogical literature as a synonym or varietal name for albite.
  • Status: Discredited; modern classification treats it simply as albite, a valid feldspar species.
  • Historical Context: Names like alvite arose in the 19th century when regional or compositional varieties of feldspars were often given separate names before structural and chemical analysis clarified their identity.

🔬 Chemical and Structural Properties (Albite)

  • Formula: NaAlSi₃O₈
  • Mineral Group: Feldspar, plagioclase series.
  • Crystal System: Triclinic.
  • Color: White, gray, bluish, greenish, or reddish depending on impurities.
  • Habit: Tabular crystals, granular aggregates, massive cleavable forms.
  • Hardness: 6–6.5 on Mohs scale.
  • Specific Gravity: ~2.6–2.65.
  • Cleavage: Perfect on {001}, very good on {010}.
  • Luster: Vitreous, pearly on cleavage surfaces.

⚙️ Geological Occurrence

  • Environment: Albite occurs in granites, pegmatites, felsic igneous rocks, and low-grade metamorphic rocks.
  • Associated Minerals: Quartz, microcline, muscovite, tourmaline.
  • Localities: Worldwide — classic occurrences in Sweden, France, USA, and many pegmatite districts.

📖 Scientific and Collector Significance

  • Petrology: Albite is a major rock-forming mineral, important in classifying igneous and metamorphic rocks.
  • Collectors: Crystals can be attractive, especially cleavelandite (a platy variety of albite).
  • Industrial Uses: Feldspar minerals, including albite, are used in ceramics, glassmaking, and as fillers.

✨ Conclusion

Alvite is an obsolete synonym for albite, the sodium-rich feldspar. While the name is no longer valid, it reflects the historical tendency to assign local or compositional variants separate names before mineral classification was standardized.

In short: Alvite = old name for albite (NaAlSi₃O₈), a common feldspar, now discredited as a separate species.

 

Alvanite

Alvanite is a rare zinc–nickel–aluminum vanadate mineral with the formula (Zn,Ni)Al₄(V⁵⁺O₃)₂(OH)₁₂·2H₂O. It was first discovered in the Karatau Mountains of Kazakhstan and is notable for its unusual combination of aluminum and vanadium in a hydrated framework.

🌍 Origins and Naming

  • Name Origin: Derived from ALuminum and VANadium in its composition.
  • Discovery: First described in 1959, approved by the IMA.
  • Type Locality: Kurumsak and Balasauskandyk districts, northwestern Karatau Mountains, Kazakhstan.

🔬 Chemical and Structural Properties

  • Formula: (Zn,Ni)Al₄(V⁵⁺O₃)₂(OH)₁₂·2H₂O
  • Crystal System: Monoclinic, point group 2/m.
  • Appearance:
    • Color: Pale bluish-green to bluish-black.
    • Habit: Thin hexagonal platelets, micaceous aggregates.
    • Luster: Vitreous to pearly.
    • Streak: White.
  • Hardness: 3–3.5 on Mohs scale.
  • Specific Gravity: ~2.49.
  • Optical Properties: Biaxial (–), semitransparent, with strong dispersion.

⚙️ Geological Occurrence

  • Environment: Found in the oxidation zones of vanadium-bearing clay–anthraxolite horizons.
  • Associated Minerals: Often occurs with other vanadates and secondary oxidation products.
  • Localities:
    • Karatau Mountains, Kazakhstan (type locality).
    • Rarely reported elsewhere; considered a very uncommon mineral.

📖 Scientific and Collector Significance

  • Petrology: Important for understanding vanadium mineral paragenesis in oxidized ore deposits.
  • Collectors: Rare and delicate; specimens are valued academically rather than aesthetically.
  • Industrial Note: No commercial use; significance lies in its rarity and unusual chemistry.

✨ Conclusion

Alvanite is a rare vanadate mineral combining Zn, Ni, Al, and V, first discovered in Kazakhstan. Its micaceous bluish-green crystals are scientifically important for vanadium mineralogy but remain a collector’s curiosity rather than an economic resource.

In short: Alvanite = rare Zn–Ni–Al vanadate, monoclinic, bluish-green, first found in Karatau Mountains, Kazakhstan.

 

Alunogen

Alunogen is a hydrated aluminum sulfate mineral, Al₂(SO₄)₃·17H₂O. It is one of the most water-rich sulfates known, forming delicate fibrous crystals in oxidized environments.

🌍 Origins and Naming

  • Name Origin: From alum (due to its sulfate chemistry) + -gen (“producer”), reflecting its relation to alum salts.
  • Discovery: First described in the early 19th century.
  • Type Locality: Likely from European mining districts where sulfide ores oxidize.

🔬 Chemical and Structural Properties

  • Formula: Al₂(SO₄)₃·17H₂O
  • Mineral Group: Sulfates.
  • Crystal System: Triclinic.
  • Color: Colorless to white; sometimes pale yellow or pink.
  • Habit: Fine fibrous crystals, crusts, or efflorescences.
  • Hardness: ~1.5–2 on Mohs scale (very soft).
  • Specific Gravity: ~1.7–1.8 (light due to high hydration).
  • Luster: Silky to vitreous.
  • Streak: White.

⚙️ Geological Occurrence

  • Formation: Secondary mineral formed by oxidation of sulfide ores (especially pyrite).
  • Environment: Found in mine walls, dumps, and oxidized zones where acidic waters evaporate.
  • Associated Minerals: Halotrichite, pickeringite, melanterite, gypsum, aluminite.
  • Localities:
    • Freiberg, Saxony, Germany.
    • Numerous mining districts in Europe and North America.

📖 Scientific and Collector Significance

  • Petrology: Indicator of highly acidic, sulfate-rich environments.
  • Collectors: Attractive silky fibrous crystals can be delicate but prized; often ephemeral due to instability.
  • Industrial Note: No commercial use; mainly of academic and collector interest.

✨ Conclusion

Alunogen is a highly hydrated aluminum sulfate, forming silky fibrous crystals in oxidized sulfide deposits. It is scientifically important as an indicator of acid mine environments and prized by collectors for its delicate appearance, though it is unstable and has no industrial role.

In short: Alunogen = Al₂(SO₄)₃·17H₂O, fibrous hydrated sulfate, secondary mineral in oxidized sulfide zones.

 

Alunite

Alunite is a hydrated aluminum potassium sulfate mineral, KAl₃(SO₄)₂(OH)₆. It is a classic sulfate mineral, often forming in oxidized zones of sulfide deposits and in volcanic environments.

🌍 Origins and Naming

  • Name Origin: From alum, due to its chemical relationship to alum salts.
  • Discovery: Known since antiquity; formally described in the 19th century.
  • Type Locality: Alunite was first identified near Tolfa, Italy.

🔬 Chemical and Structural Properties

  • Formula: KAl₃(SO₄)₂(OH)₆
  • Mineral Group: Alunite supergroup (includes jarosite and related minerals).
  • Crystal System: Trigonal.
  • Color: White, gray, pink, reddish, or yellowish.
  • Habit: Tabular crystals, granular masses, or earthy aggregates.
  • Hardness: ~3.5–4 on Mohs scale.
  • Specific Gravity: ~2.6–2.8.
  • Luster: Vitreous to pearly.
  • Streak: White.

⚙️ Geological Occurrence

  • Formation:
    • In oxidized zones of sulfide ore deposits.
    • In volcanic fumaroles and altered volcanic rocks.
    • By hydrothermal alteration of feldspar-rich rocks.
  • Associated Minerals: Jarosite, kaolinite, pyrite, gypsum.
  • Localities:
    • Tolfa, Italy (classic locality).
    • Goldfield, Nevada, USA.
    • Chile, Australia, and many volcanic districts worldwide.

📖 Scientific and Industrial Significance

  • Petrology: Indicator of hydrothermal alteration and acid-sulfate environments.
  • Industrial Uses:
    • Historically used as a source of alum (KAl(SO₄)₂·12H₂O).
    • Minor use in fertilizers and chemical industries.
  • Collectors: Attractive specimens can show pinkish tabular crystals, though massive forms are more common.

✨ Conclusion

Alunite is a hydrated aluminum potassium sulfate, forming in oxidized and volcanic environments. It is scientifically important as an alteration indicator and historically significant as a source of alum, though today it is mainly of academic and collector interest.

In short: Alunite = KAl₃(SO₄)₂(OH)₆, trigonal sulfate, alteration mineral, historically used for alum production.

 

Alumogel

Alumogel is not a formally recognized mineral species but rather an obsolete name applied to ill‑defined, gel‑like hydrous aluminum oxides. It is best thought of as a transitional or amorphous phase related to minerals like allophane and aluminite.

🌍 Origins and Naming

  • Name Origin: From alum (aluminum) + gel, describing its soft, gelatinous appearance.
  • Status: Not approved by the International Mineralogical Association (IMA).
  • Historical Context: Used in older literature to describe fine-grained, hydrated aluminum oxides found in bauxite deposits and oxidation zones.

🔬 Chemical and Structural Properties

  • Composition: Hydrous aluminum oxides, poorly defined.
  • Structure: Amorphous or gel-like; lacks long-range crystallinity.
  • Appearance: White to pale earthy masses, often resembling clays or gels.
  • Associations: Frequently occurs with aluminite (Al₂SO₄(OH)₄·7H₂O) and allophane (Al₂O₃·(SiO₂)₁.₃–₂·2.5–3H₂O).

⚙️ Geological Occurrence

  • Found in bauxite deposits and oxidized ore zones, where aluminum-bearing minerals undergo hydration and alteration.
  • Localities: Reported from Zlaté Hory, Jeseník District, Olomouc Region, Czech Republic.
  • Formation: Secondary product of weathering and alteration of aluminum-rich rocks.

📖 Scientific and Collector Significance

  • Petrology: Illustrates transitional phases between crystalline aluminum hydroxides (like gibbsite) and amorphous aluminosilicates (like allophane).
  • Collectors: Rarely collected; specimens are usually unattractive earthy masses.
  • Modern Status: Considered a non-species or descriptive term rather than a valid mineral.

✨ Conclusion

Alumogel is an obsolete descriptive name for gel-like hydrous aluminum oxides, typically found in bauxite or oxidized deposits. It is scientifically interesting as a transitional phase but has no standing as a distinct mineral species today.

In short: Alumogel = obsolete name, gel-like hydrous aluminum oxides, related to allophane and aluminite, found in bauxite deposits.

Sources:

You can explore more details on Mindat’s alumogel entry.

Alumocalcite

Alumocalcite is an obsolete mineral name historically applied to a hydrated calcium–aluminum carbonate. It is no longer recognized as a distinct species by the International Mineralogical Association (IMA), but appears in older mineralogical literature as a synonym or misidentification.

🌍 Origins and Naming

  • Name Origin: From its composition — alumo- (aluminum) + calcite (calcium carbonate).
  • Status: Obsolete; modern mineralogy does not treat alumocalcite as a valid species.
  • Historical Context: Used in the 19th century to describe earthy, white carbonate-rich material containing both calcium and aluminum.

🔬 Chemical and Structural Properties

  • Approximate Composition: Hydrated calcium–aluminum carbonate.
  • Related Minerals:
    • Hydrated aluminum carbonates such as dawsonite (NaAlCO₃(OH)₂).
    • Calcium carbonates like calcite (CaCO₃).
  • Appearance: White, earthy, clay-like masses.
  • Crystal System: Poorly defined; often amorphous or cryptocrystalline.
  • Hardness: Soft, clay-like.
  • Specific Gravity: Low, reflecting hydration.

⚙️ Geological Occurrence

  • Reported from secondary deposits where aluminum-bearing solutions interacted with carbonate rocks.
  • Often confused with mixtures of calcite, gibbsite (Al(OH)₃), or other hydrated aluminum phases.
  • Rarely identified in modern mineralogical studies due to its instability and mixed composition.

📖 Scientific and Collector Significance

  • Petrology: Illustrates early attempts to classify mixed aluminum–calcium carbonates.
  • Collectors: Not recognized today; specimens labeled “alumocalcite” are usually reclassified as mixtures or better-defined minerals.
  • Modern Status: Considered a discredited name or synonym, with no standing in current mineral taxonomy.

✨ Conclusion

Alumocalcite is an obsolete name for a hydrated calcium–aluminum carbonate, historically described but not recognized today. It represents an early stage in mineral classification, where mixed phases were often given distinct names before structural and chemical analysis clarified their identity.

In short: Alumocalcite = obsolete hydrated Ca–Al carbonate name, now discredited, historically used in 19th-century mineralogy.