Author: j5rson

Chief curmudgeon.

Alabaster

Alabaster is a fine-grained, translucent variety of gypsum (CaSO₄·2H₂O), historically prized for carving and decorative art. It has been used for thousands of years in sculpture, architecture, and ornamental objects due to its softness and luminous quality.

🌍 Origins and Naming

  • Name Origin: From Greek alabastros, originally referring to vessels made of alabaster.
  • Type: A rock term, not a distinct mineral species—most alabaster is gypsum, though historically calcite varieties were also called alabaster.
  • Appearance: White to cream, sometimes tinted with yellows, pinks, or browns.

🔬 Properties

  • Composition: Calcium sulfate dihydrate (CaSO₄·2H₂O).
  • Crystal System: Monoclinic (gypsum).
  • Texture: Fine-grained, massive, often translucent.
  • Hardness: 1.5–2 on Mohs scale (very soft, easily scratched with a fingernail).
  • Specific Gravity: ~2.3
  • Luster: Waxy to pearly.

⚙️ Geological Occurrence

  • Forms in evaporite deposits, where saline waters evaporate leaving gypsum layers.
  • Commonly found in sedimentary basins worldwide.
  • Major sources: Italy, Egypt, England, Spain, and the United States.

🏛️ Historical and Cultural Significance

  • Ancient Egypt: Used for canopic jars, vessels, and tomb decoration.
  • Medieval Europe: Extensively carved into altarpieces, effigies, and church decorations.
  • Modern Use: Sculptures, lamps, decorative panels, and small ornamental carvings.
  • Symbolism: Associated with purity, light, and delicacy.

✨ Conclusion

Alabaster is a soft, fine-grained gypsum rock, treasured for its translucence and ease of carving. From ancient Egyptian vessels to medieval church effigies and modern decorative art, it remains one of the most historically significant ornamental stones.

In short: Alabaster = soft, translucent gypsum, used for carving and decoration since antiquity.

 

Alabandite

Alabandite is a rare manganese sulfide mineral (MnS), typically found in hydrothermal deposits and occasionally in meteorites. It is scientifically important as one of the few naturally occurring simple sulfides of manganese.

🌍 Origins and Naming

  • Name Origin: Named after Alabanda, a town in Turkey, where it was first described in 1784.
  • Type Locality: Alabanda, Turkey.

🔬 Chemical and Structural Properties

  • Formula: MnS
  • Crystal System: Cubic (isometric)
  • Color: Black, brownish-black, sometimes greenish-black
  • Habit: Massive, granular, or rarely cubic crystals
  • Hardness: 3.5–4 on Mohs scale
  • Specific Gravity: ~4.0
  • Luster: Metallic to submetallic
  • Streak: Greenish-gray

⚙️ Geological Occurrence

  • Found in hydrothermal veins and manganese-rich deposits.
  • Associated Minerals: Galena, sphalerite, pyrite, chalcopyrite, rhodochrosite.
  • Localities:
    • Turkey (type locality)
    • Japan
    • Sweden (Långban deposit)
    • USA (Montana, Colorado)
    • Found in some meteorites, making it of interest in planetary mineralogy.

📖 Scientific and Collector Significance

  • Petrology: Important for understanding manganese geochemistry in sulfide systems.
  • Collectors: Rare, usually massive and dark, but valued for its rarity and meteorite associations.
  • Economic Note: Not a major ore of manganese due to scarcity, but academically significant.

⚠️ Safety Considerations

Contains sulfide, which can release toxic gases if heated or altered. Specimens are safe when intact but should be handled with care.

✨ Conclusion

Alabandite is a rare manganese sulfide mineral (MnS), first described in Turkey, found in hydrothermal deposits and meteorites. While not visually striking, it is scientifically important for understanding manganese sulfide chemistry and prized by collectors for its rarity.

In short: Alabandite = MnS, a rare black manganese sulfide mineral, found in hydrothermal veins and meteorites.

 

Aksaite

Aksaite is a very rare borate mineral, specifically a hydrated calcium–magnesium borate. It is scientifically notable because it represents one of the uncommon borate species found in evaporite deposits.

🌍 Origins and Naming

  • Name Origin: Named after the Ak-Sai deposit in Kyrgyzstan, where it was first discovered.
  • Type Locality: Ak-Sai borate deposit, Kyrgyzstan.
  • Discovery: Described in the mid‑20th century during studies of borate-rich evaporites.

🔬 Chemical and Structural Properties

  • Formula: CaMg[B₆O₇(OH)₆]·2H₂O
  • Mineral Group: Borates
  • Crystal System: Monoclinic
  • Color: White to colorless, sometimes pale gray
  • Habit: Fibrous, acicular crystals or massive aggregates
  • Hardness: ~3–4 on Mohs scale
  • Specific Gravity: ~2.0–2.2 (light due to boron content)
  • Luster: Vitreous to silky
  • Streak: White

⚙️ Geological Occurrence

  • Found in borate-rich evaporite deposits, often associated with:
    • Ulexite
    • Inyoite
    • Colemanite
  • Forms under low-temperature evaporitic conditions where boron-rich fluids precipitate calcium–magnesium borates.

📖 Scientific and Collector Significance

  • Petrology: Important for understanding boron geochemistry in evaporite basins.
  • Collectors: Rare and delicate, usually only available from type localities.
  • Economic Note: Not an ore mineral, but contributes to knowledge of borate mineral diversity.

✨ Conclusion

Aksaite is a rare hydrated calcium–magnesium borate, first described in Kyrgyzstan, occurring in evaporite deposits alongside other borates. Though not economically significant, it is scientifically valuable for understanding boron mineralogy and prized by collectors for its rarity.

In short: Aksaite = rare Ca–Mg borate, fibrous crystals, first found in Kyrgyzstan’s borate deposits.

Akrochordite

Akrochordite is a rare hydrated manganese arsenate mineral, part of the adelite–descloizite group. It is scientifically notable for its unusual chemistry and its occurrence in oxidized arsenic-rich environments.

🌍 Origins and Naming

  • Name Origin: From Greek akrochordon (“wart”), referring to its typical wart-like crystal aggregates.
  • First Described: 1955, from Långban, Sweden (a classic locality for rare arsenates).
  • Type Locality: Långban mine, Värmland, Sweden.

🔬 Chemical and Structural Properties

  • Formula: Mn₅(AsO₄)₂(OH)₄·4H₂O
  • Mineral Group: Arsenates (adelite–descloizite group)
  • Crystal System: Monoclinic
  • Color: Brownish-red, reddish-orange, sometimes pinkish
  • Habit: Small wart-like aggregates, crusts, or granular masses
  • Hardness: ~3.5–4 on Mohs scale
  • Specific Gravity: ~3.6
  • Luster: Vitreous to dull
  • Streak: Pale brown

⚙️ Geological Occurrence

  • Forms in oxidized zones of manganese-arsenic deposits.
  • Associated Minerals: Allactite, hausmannite, jacobsite, and other rare arsenates.
  • Localities:
    • Långban, Sweden (type locality, famous for rare arsenates)
    • Other manganese-rich deposits in Austria, Germany, and the USA (Franklin, New Jersey).

📖 Scientific and Collector Significance

  • Petrology: Important for understanding arsenate mineral paragenesis in manganese-rich environments.
  • Collectors: Rare and usually found as small aggregates, but valued for its unusual reddish coloration and rarity.
  • Economic Note: No commercial use due to rarity, but academically significant.

⚠️ Safety Considerations

Contains arsenic, so specimens should be handled with care—avoid inhaling dust or ingesting particles, and wash hands after handling.

✨ Conclusion

Akrochordite is a rare manganese arsenate mineral, first described in Sweden, recognized for its wart-like reddish aggregates. While not economically important, it is prized by collectors and mineralogists for its rarity and contribution to understanding arsenate mineralogy.

In short: Akrochordite = Mn arsenate, reddish wart-like aggregates, rare, first found at Långban, Sweden.

 

Akhtenskite

Akhtenskite is a rare manganese oxide mineral (MnO₂), specifically the hexagonal polymorph of manganese dioxide. It was first described in Russia in 1979 and is scientifically important as a structural variant of MnO₂, distinct from the more common pyrolusite (orthorhombic MnO₂).

🌍 Origins and Naming

  • Name Origin: Named after the Akhtensk deposit in the southern Ural Mountains, Russia, where it was first discovered.
  • Type Locality: Akhtensk brown ironstone deposit, Kusinsky District, Chelyabinsk Oblast, Russia.
  • Other Localities: Mt. Zarod, Sikhote-Alin Mountains, and Primorskiy Krai, Russia.

🔬 Chemical and Structural Properties

  • Formula: MnO₂ (ε‑Mn⁴⁺O₂)
  • Crystal System: Hexagonal (space group P6₃/mmc)
  • Color: Light gray to black
  • Habit: Flaky polycrystalline aggregates, platy crystals, sometimes forming rows at 120°
  • Cleavage: Distinct on {001}
  • Hardness: Not well defined, but similar to other Mn oxides (~2–3 Mohs)
  • Specific Gravity: ~4.78 (calculated)
  • Streak: Black
  • Optical Properties: Opaque, uniaxial

⚙️ Geological Occurrence

  • Found in ironstone deposits and ferromanganese incrustations.
  • Often occurs in mixtures with other manganese oxides (like psilomelane).
  • May form through low-temperature alteration processes, sometimes bacterially mediated.

📖 Scientific and Collector Significance

  • Polymorphs: Akhtenskite is a polymorph of pyrolusite and ramsdellite, all MnO₂ but with different crystal structures.
  • Environmental Role: Synthetic akhtenskite has been studied for arsenic removal in water treatment, showing applied significance.
  • Collectors: Rare and usually microscopic, so not a major collector’s mineral, but valued academically.

✨ Conclusion

Akhtenskite is a hexagonal manganese dioxide polymorph, first described in Russia, found in ironstone deposits and manganese-rich environments. While visually modest, it is scientifically important for understanding MnO₂ polymorphism and has potential environmental applications.

In short: Akhtenskite = hexagonal MnO₂, rare manganese oxide polymorph, first found in Russia, important in geochemistry.

 

Akaganeite

Akaganeite is a rare iron oxyhydroxide mineral, chemically β‑FeO(OH,Cl), notable for containing chloride ions within its crystal structure. It is scientifically important because it forms under specific oxidizing conditions and is often associated with weathering of iron-bearing materials, meteorites, and even archaeological artifacts.

🌍 Origins and Naming

  • Name Origin: Named after the Akagane mine in Japan, where it was first described in 1962.
  • Type Locality: Akagane mine, Japan.
  • Group: Iron oxyhydroxides (related to goethite and lepidocrocite).

🔬 Chemical and Structural Properties

  • Formula: Fe³⁺O(OH,Cl)
  • Crystal System: Monoclinic
  • Color: Brown, yellow-brown, sometimes reddish
  • Habit: Acicular (needle-like), fibrous, or massive aggregates
  • Hardness: ~5 on Mohs scale
  • Specific Gravity: ~3.5–3.8
  • Luster: Earthy to submetallic
  • Streak: Yellowish brown

⚙️ Geological and Environmental Occurrence

  • Forms in oxidized iron-bearing environments, especially where chloride ions are present.
  • Common Settings:
    • Weathering of pyrite and other sulfides
    • Corrosion products of iron and steel (important in archaeology and conservation)
    • Found in meteorites (Martian meteorites and lunar samples have reported akaganeite)
  • Associated Minerals: Goethite, lepidocrocite, hematite.

📖 Scientific and Collector Significance

  • Petrology: Indicates chloride-rich oxidizing conditions.
  • Planetary Science: Detected in Martian soils and meteorites, providing clues about water and chloride chemistry on Mars.
  • Archaeology: Appears as a corrosion product on ancient iron artifacts, complicating conservation efforts.
  • Collectors: Rarely collected due to its earthy appearance, but scientifically prized.

✨ Conclusion

Akaganeite is a chloride-bearing iron oxyhydroxide, first described in Japan, now recognized in terrestrial weathering environments, meteorites, and even Martian soils. Its presence is a marker of chloride-rich oxidation and has implications for geology, planetary science, and artifact preservation.

In short: Akaganeite = β‑FeO(OH,Cl), a chloride-bearing iron oxyhydroxide found in oxidized environments, meteorites, and artifacts.

 

Ajkaite

Ajkaite is a very rare sulfosalt mineral composed of copper, tellurium, and bismuth. It is scientifically notable because it represents a complex Cu–Te–Bi sulfide phase, found in specialized hydrothermal environments.

🌍 Origins and Naming

  • Name Origin: Named after the Ajka mining district in Hungary, where it was first discovered.
  • Type Locality: Ajka, Veszprém County, Hungary.

🔬 Chemical and Structural Properties

  • Formula: Cu₇TeBi₅S₁₃
  • Mineral Group: Sulfosalts (complex sulfide minerals containing multiple metals).
  • Crystal System: Orthorhombic
  • Color: Steel-gray to black
  • Habit: Typically massive or granular; crystals are rare
  • Hardness: ~2.5–3 on Mohs scale
  • Specific Gravity: ~6.5–7.0 (very dense due to Bi and Te content)
  • Luster: Metallic
  • Streak: Black

⚙️ Geological Occurrence

Ajkaite forms in hydrothermal veins rich in bismuth, copper, and tellurium.

  • Associated Minerals: Tetradymite, bismuthinite, emplectite, and other Bi–Te–Cu sulfides.
  • Localities:
    • Ajka, Hungary (type locality)
    • Rare occurrences in other tellurium-rich hydrothermal deposits worldwide

📖 Scientific and Collector Significance

  • Petrology: Important for understanding the geochemistry of tellurium-bearing hydrothermal systems.
  • Collectors: Extremely rare and usually unattractive visually, but valued for rarity and locality.
  • Economic Note: Not an ore mineral due to scarcity, but contributes to knowledge of Bi–Te–Cu mineralization.

⚠️ Safety Considerations

Contains bismuth and tellurium sulfides; while not highly toxic, handling should be cautious, avoiding dust inhalation.

✨ Conclusion

Ajkaite is a rare copper–tellurium–bismuth sulfosalt, first described in Hungary. Though not visually striking, it is scientifically important for understanding tellurium-rich hydrothermal mineralization and prized by collectors for its rarity and locality.

In short: Ajkaite is a rare Cu–Te–Bi sulfosalt mineral, discovered in Ajka, Hungary, significant for geochemistry.

 

Aikinite

Aikinite is a rare sulfosalt mineral composed of lead, copper, and bismuth sulfide. It is scientifically significant as part of the bismuth-bearing sulfosalt family and is often studied for its complex chemistry and paragenesis in hydrothermal deposits.

🌍 Origins and Naming

  • Name Origin: Named in 1825 after Arthur Aikin (1773–1854), an English geologist and chemist.
  • Type Locality: Cornwall, England.

🔬 Chemical and Structural Properties

  • Formula: PbCuBiS₃
  • Mineral Group: Sulfosalts
  • Crystal System: Orthorhombic
  • Color: Lead-gray to steel-gray
  • Habit: Massive, granular, or elongated crystals (rarely well-formed)
  • Hardness: 2–2.5 on Mohs scale (very soft)
  • Specific Gravity: ~6.1–6.8 (dense due to Pb and Bi content)
  • Luster: Metallic
  • Streak: Black

⚙️ Geological Occurrence

Aikinite typically forms in hydrothermal veins rich in lead, copper, and bismuth.

  • Associated Minerals: Galena, chalcopyrite, bismuthinite, tetrahedrite, and other sulfosalts.
  • Localities:
    • Cornwall, England (classic locality)
    • Bolivia
    • Russia (Siberia)
    • Australia
    • USA (Colorado, Nevada)

📖 Scientific and Collector Significance

  • Petrology: Important for understanding bismuth-bearing sulfosalt mineralization.
  • Collectors: Rare and usually unattractive visually (dark metallic masses), but valued for rarity and historical significance.
  • Economic Note: Minor ore of bismuth, copper, and lead, though not a major commercial source.

⚠️ Safety Considerations

Contains lead and bismuth, so handling requires care. Wash hands after contact and avoid inhaling dust.

✨ Conclusion

Aikinite is a rare lead–copper–bismuth sulfosalt, first described in Cornwall, England. While not visually striking, it is scientifically important for understanding sulfosalt mineralogy and prized by collectors for its rarity and historical context.

In short: Aikinite is a rare Pb–Cu–Bi sulfosalt mineral, metallic gray, found in hydrothermal veins.

Ahlfeldite

Ahlfeldite is a rare nickel selenite mineral, part of the selenite group, and notable for its bright green coloration. It is scientifically interesting because it represents nickel’s incorporation into selenium-bearing secondary minerals, typically forming in the oxidation zones of nickel-selenium deposits.

🌍 Origins and Naming

  • Name Origin: Named in 1950 after Dr. Friedrich Ahlfeld (1892–1982), a German geologist known for his work in South America.
  • Type Locality: Sierra de Cachimbo, Bolivia.

🔬 Chemical and Structural Properties

  • Formula: NiSeO₃·2H₂O
  • Mineral Group: Selenites
  • Crystal System: Monoclinic
  • Color: Bright emerald-green to bluish-green
  • Habit: Fibrous crusts, earthy coatings, or fine-grained aggregates
  • Hardness: ~2–3 on Mohs scale (soft)
  • Specific Gravity: ~3.8–4.0
  • Luster: Vitreous to silky
  • Streak: Greenish

⚙️ Geological Occurrence

Ahlfeldite forms as a secondary mineral in the oxidation zones of nickel-selenium deposits.

  • Associated Minerals: Chalcomenite (Cu selenite), cobaltomenite (Co selenite), and other secondary selenium minerals.
  • Localities:
    • Bolivia (type locality)
    • Chile
    • Argentina
    • Rare occurrences in other selenium-rich deposits worldwide

📖 Scientific and Collector Significance

  • Petrology: Provides insight into selenium geochemistry and nickel’s role in secondary mineral formation.
  • Collectors: Attractive green coloration makes it desirable, though specimens are rare and often small.
  • Economic Note: Not an ore of nickel or selenium due to rarity, but scientifically valuable.

⚠️ Safety Considerations

Contains selenium, which can be toxic. Handling requires care—avoid inhaling dust or ingesting particles, and wash hands after contact.

✨ Conclusion

Ahlfeldite is a rare nickel selenite mineral, first described in Bolivia, valued for its vivid green color and scientific importance in understanding selenium-rich oxidation environments. Though not economically significant, it remains a collector’s curiosity and a geochemical marker.

In short: Ahlfeldite is a rare green nickel selenite, first found in Bolivia, prized for rarity and scientific value.

 

Aguilarite

Aguilarite is a rare silver sulfosalt mineral, chemically a silver selenide-sulfide, and part of the acanthite–naumannite series. It is scientifically important because it represents the selenium-rich endmember of this series, bridging silver sulfide (Ag₂S) and silver selenide (Ag₂Se).

🌍 Origins and Naming

  • Name Origin: Named in 1891 after P. Aguilar, a mine director in Guanajuato, Mexico, where the mineral was first described.
  • Type Locality: Guanajuato mining district, Mexico.

🔬 Chemical and Structural Properties

  • Formula: Ag₄SeS (sometimes written as Ag₂S·Ag₂Se)
  • Mineral Group: Sulfosalts (silver selenide-sulfide series)
  • Crystal System: Monoclinic
  • Color: Dark gray to black, metallic
  • Habit: Typically massive or granular, rarely well-formed crystals
  • Hardness: 2–2.5 on Mohs scale (very soft)
  • Specific Gravity: ~6.7–6.9 (very dense due to silver content)
  • Luster: Metallic
  • Streak: Black

⚙️ Geological Occurrence

Aguilarite occurs in hydrothermal silver deposits, often associated with other silver minerals.

  • Associated Minerals: Acanthite (Ag₂S), naumannite (Ag₂Se), proustite, pyrargyrite, galena, chalcopyrite.
  • Localities:
    • Guanajuato, Mexico (type locality)
    • Other silver-rich deposits in Germany, Chile, and the USA (Colorado, Nevada).

📖 Scientific and Collector Significance

  • Petrology: Important for understanding selenium substitution in silver sulfide systems.
  • Collectors: Rare and usually unattractive visually (dark metallic masses), but valued for rarity.
  • Economic Note: Minor ore of silver, though not a major commercial source due to scarcity.

⚠️ Safety Considerations

Contains selenium, which can be toxic in high concentrations. Handling requires care, though risk is minimal for solid specimens.

✨ Conclusion

Aguilarite is a rare silver selenide-sulfide mineral, first described in Mexico, scientifically significant as the selenium-rich endmember of the acanthite–naumannite series. While not visually striking, it is prized by collectors and mineralogists for its rarity and geochemical importance.

In short: Aguilarite is a rare silver sulfosalt (Ag₄SeS), bridging silver sulfide and silver selenide, first found in Guanajuato, Mexico.