Author: j5rson

Chief curmudgeon.

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.

 

Aluminum

Aluminum (Al) is a lightweight, silvery-white metal that is the most abundant metallic element in Earth’s crust. It is central to modern industry, prized for its combination of low density, corrosion resistance, and versatility.

🌍 Origins and Naming

  • Name Origin: From alumen (Latin for alum), a compound known since antiquity.
  • Discovery: Isolated as a pure metal in 1825 by Hans Christian Ørsted, refined further by Friedrich Wöhler in 1827.
  • Occurrence: Found in minerals like bauxite (primary ore), cryolite, and feldspars.

🔬 Chemical and Physical Properties

  • Symbol: Al
  • Atomic Number: 13
  • Atomic Weight: ~26.98
  • Crystal Structure: Face-centered cubic (FCC).
  • Density: 2.70 g/cm³ (about one-third that of steel).
  • Melting Point: ~660 °C.
  • Color: Silvery-white, metallic.
  • Reactivity: Forms a protective oxide layer (Al₂O₃) that prevents further corrosion.

⚙️ Industrial Production

  • Ore: Bauxite → processed via the Bayer process to alumina (Al₂O₃).
  • Metal Extraction: Alumina reduced to aluminum metal by Hall–Héroult process (electrolysis in molten cryolite).
  • Global Significance: One of the most produced metals worldwide.

🏭 Applications

  • Transportation: Aircraft, automobiles, ships (lightweight, strong alloys).
  • Construction: Window frames, roofing, siding, structural components.
  • Packaging: Foil, cans, containers.
  • Electrical: Conductors, transmission lines (good conductivity, low weight).
  • Consumer Goods: Appliances, electronics, sporting equipment.
  • Specialty Alloys: Aluminum–lithium alloys in aerospace, aluminum–magnesium alloys in marine use.

📖 Scientific and Environmental Significance

  • Materials Science: Aluminum alloys balance strength, ductility, and corrosion resistance.
  • Recycling: Highly recyclable; requires only ~5% of the energy compared to primary production.
  • Environmental Note: Mining bauxite and refining alumina have ecological impacts, but recycling mitigates them.

✨ Conclusion

Aluminum is a lightweight, corrosion-resistant, and versatile metal, essential to modern life from airplanes to soda cans. Its abundance, recyclability, and adaptability make it one of the most important industrial materials of the 20th and 21st centuries.

In short: Aluminum = abundant, lightweight, corrosion-resistant metal, produced from bauxite, vital in industry and everyday life.

 

Aluminite

Aluminite is a rare hydrous aluminum sulfate mineral, Al₂SO₄(OH)₄·7H₂O. It is soft, earthy, and typically forms as a secondary mineral in oxidized environments.

🌍 Origins and Naming

  • Name Origin: From its aluminum content.
  • Discovery: First described in 1807.
  • Type Locality: Likely from England, where early specimens were studied.

🔬 Chemical and Structural Properties

  • Formula: Al₂SO₄(OH)₄·7H₂O
  • Mineral Group: Sulfates.
  • Crystal System: Monoclinic (though crystals are extremely rare; usually earthy masses).
  • Color: White, grayish, sometimes pale yellow.
  • Habit: Earthy, clay-like masses; rarely fibrous or compact.
  • Hardness: ~1.5–2 on Mohs scale (very soft).
  • Specific Gravity: ~1.7–1.8 (light due to hydration).
  • Luster: Dull to earthy.
  • Streak: White.

⚙️ Geological Occurrence

  • Forms as a secondary mineral in clay deposits, lignite beds, and oxidized sulfide veins.
  • Associated Minerals: Gibbsite, alunogen, gypsum, halotrichite, and other hydrated sulfates.
  • Localities:
    • England (classic occurrences).
    • Germany.
    • USA (notably in coal-bearing regions).

📖 Scientific and Collector Significance

  • Petrology: Illustrates hydration and alteration processes of aluminum-bearing sulfates.
  • Collectors: Rarely aesthetic; valued academically for its rarity and paragenesis.
  • Industrial Note: No commercial use; too soft and unstable.

✨ Conclusion

Aluminite is a soft, hydrous aluminum sulfate, usually forming earthy white masses in oxidized environments. It is scientifically interesting as a secondary mineral but remains a collector’s curiosity rather than an economic resource.

In short: Aluminite = Al₂SO₄(OH)₄·7H₂O, soft earthy sulfate, rare, first described in 1807.

 

Aluminate

Aluminate refers to compounds containing the anion [AlO₂]⁻ or related aluminum–oxygen units. These are typically salts or complex ions formed when aluminum oxide or hydroxide reacts with bases. The term is used both in mineralogy and industrial chemistry.

🌍 Origins and Naming

  • Name Origin: From alumen (Latin for alum) + -ate, indicating a salt of aluminum.
  • Context: “Aluminate” is not a single mineral but a class of compounds and ions.

🔬 Chemical and Structural Properties

  • General Formula: M[AlO₂] or MAlO₂, where M = alkali or alkaline earth cation (Na, K, Ca, etc.).
  • Common Forms:
    • Sodium aluminate (NaAlO₂): Industrially important.
    • Calcium aluminate (CaAl₂O₄, CaAl₄O₇, etc.): Found in cements.
    • Potassium aluminate (KAlO₂).
  • Structure: Often polymeric, with Al³⁺ in tetrahedral coordination with oxygen.
  • Appearance: White crystalline solids or powders.

⚙️ Geological and Industrial Occurrence

  • Mineralogical Context: Aluminate phases occur in high-temperature environments, such as cement clinker and refractory materials.
  • Industrial Production:
    • Sodium aluminate is made by dissolving alumina in sodium hydroxide.
    • Calcium aluminates are produced in alumina–lime systems for special cements.
  • Applications:
    • Water Treatment: Sodium aluminate as a coagulant.
    • Cement Industry: Calcium aluminates in high-performance cements.
    • Paper Industry: Used in sizing and coatings.
    • Catalysis: Aluminate phases as supports or intermediates.

📖 Scientific and Collector Significance

  • Chemistry: Illustrates how aluminum forms oxyanions under strongly basic conditions.
  • Materials Science: Aluminates are critical in refractories, ceramics, and cement chemistry.
  • Collectors: Not typically collected as minerals; more relevant in industrial and synthetic contexts.

✨ Conclusion

Aluminate is a general term for aluminum–oxygen salts and ions, ranging from sodium aluminate in water treatment to calcium aluminates in cement. While not a distinct mineral species, aluminates are central to industrial chemistry and materials science.

In short: Aluminate = aluminum–oxygen salts/ions, key in cements, water treatment, and industrial chemistry.

 

Alumina trihydrate

Alumina trihydrate (ATH) is the hydrated form of aluminum oxide, with the formula Al(OH)₃. It is a key industrial chemical, widely used in flame retardants, fillers, and as the precursor to calcined alumina.

🌍 Origins and Naming

  • Name Origin: “Alumina trihydrate” reflects its composition: aluminum oxide combined with three molecules of water.
  • Mineral Equivalent: Gibbsite (Al(OH)₃) is the natural mineral form.
  • Industrial Source: Extracted from bauxite ore via the Bayer process, where alumina trihydrate is precipitated before calcination.

🔬 Chemical and Structural Properties

  • Formula: Al(OH)₃
  • Crystal System: Monoclinic (gibbsite).
  • Color: White, powdery when processed; crystalline gibbsite is colorless to white.
  • Hardness: ~2.5–3 on Mohs scale.
  • Density: ~2.4 g/cm³.
  • Stability: Decomposes upon heating (~180–200 °C), releasing water and forming alumina (Al₂O₃).

⚙️ Industrial and Technological Uses

  • Flame Retardants: ATH releases water vapor when heated, cooling the material and diluting combustible gases.
  • Fillers: Used in plastics, rubber, and paper for whiteness, opacity, and reinforcement.
  • Electrical Insulation: Improves arc resistance in polymers.
  • Ceramics & Glass: Precursor to calcined alumina for refractories and advanced ceramics.
  • Water Treatment: Sometimes used as a coagulant.

📖 Scientific and Environmental Significance

  • Materials Science: ATH is a critical intermediate in alumina production.
  • Environmental Role: Flame-retardant ATH is favored as a halogen-free alternative, reducing toxic smoke in fires.
  • Geology: Gibbsite is one of the three main aluminum hydroxide minerals in bauxite (with boehmite and diaspore).

✨ Conclusion

Alumina trihydrate (Al(OH)₃) is the hydrated precursor to alumina, naturally occurring as gibbsite and industrially vital for flame retardants, fillers, and ceramics. It bridges geology (bauxite minerals) and technology (advanced materials).

In short: Alumina trihydrate = Al(OH)₃, gibbsite, precursor to alumina, key in flame retardants and fillers.

 

Alumina

Alumina (Al₂O₃) is the oxide of aluminum, one of the most important industrial materials in the world. It occurs naturally as the mineral corundum (including ruby and sapphire varieties) and is also produced synthetically from bauxite.

🌍 Origins and Naming

  • Name Origin: From alumen (Latin for alum), reflecting its aluminum content.
  • Natural Form: Corundum (gem varieties ruby and sapphire).
  • Synthetic Form: Produced industrially via the Bayer process from bauxite ore.

🔬 Chemical and Structural Properties

  • Formula: Al₂O₃
  • Crystal System: Trigonal (corundum structure).
  • Polymorphs:
    • α-Alumina: Stable crystalline form (corundum).
    • γ, δ, θ, κ-Alumina: Metastable transition phases, often formed during calcination.
  • Color: Pure alumina is white; impurities give red (ruby), blue (sapphire), or other colors.
  • Hardness: 9 on Mohs scale (second only to diamond).
  • Density: ~3.9–4.0 g/cm³.
  • Melting Point: ~2050 °C.
  • Luster: Vitreous.

⚙️ Geological and Industrial Occurrence

  • Natural: Found as corundum in metamorphic rocks and placer deposits.
  • Industrial Production: Extracted from bauxite via Bayer process → calcined to alumina.
  • Associated Minerals: Hematite, gibbsite, boehmite, diaspore.

🏭 Applications

  • Metallurgy: Primary raw material for aluminum metal (via Hall–Héroult process).
  • Abrasives: Grinding wheels, sandpapers, blasting media.
  • Refractories: Furnace linings, crucibles, kiln furniture.
  • Ceramics: Advanced ceramics, spark plugs, substrates for electronics.
  • Gemstones: Ruby and sapphire are gem-quality alumina colored by trace elements.
  • Catalyst Supports: Used in chemical industries due to high surface stability.
  • Biomedical: Bioceramics for implants due to biocompatibility and wear resistance.

✨ Conclusion

Alumina (Al₂O₃) is both a natural mineral (corundum) and a synthetic industrial material, prized for its hardness, stability, and versatility. It underpins industries from metallurgy to electronics, while also dazzling as ruby and sapphire in gemology.

In short: Alumina = Al₂O₃, corundum in nature, Bayer process in industry, vital for metals, abrasives, ceramics, and gems.

 

Altaite

Altaite is a rare lead telluride mineral (PbTe). It is scientifically notable as one of the few naturally occurring tellurides of lead, and it often occurs in association with precious-metal tellurides in hydrothermal deposits.

🌍 Origins and Naming

  • Name Origin: Named after the Altai Mountains, Russia, where it was first discovered.
  • Discovery: Described in the late 19th century.
  • Type Locality: Altai Mountains, Siberia.

🔬 Chemical and Structural Properties

  • Formula: PbTe
  • Mineral Group: Tellurides.
  • Crystal System: Isometric (cubic).
  • Color: Lead-gray to steel-gray.
  • Habit: Granular, massive; crystals are rare.
  • Hardness: ~2.5 on Mohs scale (soft, like galena).
  • Specific Gravity: ~8.1 (very dense due to Pb content).
  • Luster: Metallic.
  • Streak: Black.

⚙️ Geological Occurrence

  • Found in hydrothermal veins, often associated with gold and silver tellurides.
  • Associated Minerals: Galena, pyrite, chalcopyrite, hessite (Ag₂Te), sylvanite, petzite, and other tellurides.
  • Localities:
    • Altai Mountains, Russia (type locality).
    • Kalgoorlie, Western Australia.
    • Colorado, USA.
    • Other precious-metal districts worldwide.

📖 Scientific and Collector Significance

  • Petrology: Important for understanding telluride mineralization in hydrothermal systems.
  • Collectors: Rare, usually unattractive massive specimens, valued for rarity and association with gold–telluride ores.
  • Economic Note: Contains lead and tellurium, but too rare to be an ore mineral. Its significance lies in its association with precious metals.

⚠️ Safety Considerations

Contains lead and tellurium, both toxic. Specimens should be handled carefully — avoid inhaling dust or ingesting particles, and wash hands after handling.

✨ Conclusion

Altaite is a rare lead telluride (PbTe), first described from the Altai Mountains. It is scientifically significant for illustrating telluride mineralization in hydrothermal veins, though it remains a collector’s curiosity rather than an economic resource.

In short: Altaite = PbTe, lead telluride, metallic, rare, first found in Altai Mountains.

 

Alstonite

Alstonite is a rare barium–calcium carbonate mineral, BaCa(CO₃)₂. It is scientifically notable as one of the few double carbonates of barium and calcium, and it occurs in low-temperature hydrothermal veins.

🌍 Origins and Naming

  • Name Origin: Named after Alston Moor, Cumbria, England, where it was first discovered.
  • Discovery: Described in 1841 by mineralogist Thomas Thomson.
  • Type Locality: Alston Moor, Cumbria, England.

🔬 Chemical and Structural Properties

  • Formula: BaCa(CO₃)₂
  • Mineral Group: Carbonates.
  • Crystal System: Trigonal.
  • Color: White, colorless, or pale shades (sometimes pinkish or grayish).
  • Habit: Tabular crystals, granular aggregates, or massive forms.
  • Hardness: ~4–4.5 on Mohs scale.
  • Specific Gravity: ~3.7–3.8.
  • Luster: Vitreous to pearly.
  • Streak: White.

⚙️ Geological Occurrence

  • Found in low-temperature hydrothermal veins, often associated with lead–zinc mineralization.
  • Associated Minerals: Baryte, calcite, witherite, fluorite, galena, sphalerite.
  • Localities:
    • Alston Moor, Cumbria, England (type locality).
    • Other occurrences in Scotland, France, and the USA.

📖 Scientific and Collector Significance

  • Petrology: Important for understanding carbonate mineral chemistry, especially Ba–Ca substitutions.
  • Collectors: Attractive tabular crystals are rare but valued; more often found as massive aggregates.
  • Economic Note: No industrial use; mainly of academic and collector interest.

✨ Conclusion

Alstonite is a rare Ba–Ca carbonate (BaCa(CO₃)₂), first described from Alston Moor, England. It is scientifically significant for illustrating double carbonate chemistry, though it remains a collector’s curiosity rather than an economic resource.

In short: Alstonite = Ba–Ca carbonate, trigonal, rare, first found at Alston Moor, England.

 

Alshedite

Alshedite is an obsolete or varietal name historically used for yttrian titanite (a yttrium-bearing variety of titanite, also called keilhauite). It is not recognized today as a distinct mineral species by the International Mineralogical Association (IMA), but it appears in older mineralogical literature and collector references.

🌍 Origins and Naming

  • Name Origin: The name “Alshedite” (sometimes spelled Alshedit) was applied to titanite specimens enriched in yttrium.
  • Type Locality: Kragerø, Telemark, Norway — a classic site for rare titanite varieties.
  • Status: Considered a synonym or varietal name; modern classification treats it as yttrian titanite (keilhauite) rather than a separate species.

🔬 Chemical and Structural Properties

  • Base Formula (Titanite): CaTiSiO₅
  • Alshedite Composition: Titanite with partial substitution of Ca²⁺ by Y³⁺ and other rare earth elements.
  • Crystal System: Monoclinic.
  • Color: Brownish, reddish-brown, or dark hues (due to Y and REE substitution).
  • Habit: Typically small prismatic crystals, often granular.
  • Hardness: ~5–5.5 on Mohs scale.
  • Specific Gravity: ~3.5–3.6 (slightly higher than pure titanite due to Y content).
  • Luster: Adamantine to resinous.

⚙️ Geological Occurrence

  • Found in alkaline igneous rocks and metamorphic deposits rich in rare earth elements.
  • Localities:
    • Kragerø, Telemark, Norway (classic occurrence).
    • Arendal, Aust-Agder, Norway.
    • Other Scandinavian pegmatites and REE-bearing rocks.
  • Associated Minerals: Zircon, allanite, monazite, and other REE-bearing silicates.

📖 Scientific and Collector Significance

  • Petrology: Illustrates how titanite incorporates rare earth elements like yttrium.
  • Collectors: Rare and usually small crystals; valued for locality and historical naming rather than aesthetics.
  • Modern Status: Today, specimens labeled “Alshedite” are classified as yttrian titanite (keilhauite).

✨ Conclusion

Alshedite is an obsolete name for yttrian titanite (keilhauite), a rare Y-bearing variety of titanite. It was first described from Norway and remains of historical interest, but modern mineralogy treats it as a titanite variety rather than a distinct species.

In short: Alshedite = old name for yttrian titanite (keilhauite), rare REE-bearing titanite variety, first found in Norway.