mineral-database/data/source/minerals/chalcedony.yaml at 11e490a3a44ba292c7d61fbb2a6c90ead5ba6464 · gemmology-dev/mineral-database · GitHub

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id: chalcedony
name: Chalcedony
crystal_system: trigonal
point_group: '32'
chemistry: SiO2
mineral_group: Quartz Group
category: Tectosilicates
hardness: 6.5-7
sg: 2.58-2.64
ri: 1.530-1.540
birefringence: null
optical_character: Aggregate
lustre: Waxy to vitreous
cleavage: None
fracture: Conchoidal
diagnostic_features: "Cryptocrystalline; waxy lustre; banded (agate) or uniform colour; lower RI than crystalline quartz"
colors:
- Blue (chalcedony)
- Red-orange (carnelian)
- Green (chrysoprase)
- Banded (agate)
- Black (onyx)
- Brown (sard)
treatments:
- Dyeing
- Heat treatment
- Sugar-acid treatment (onyx)
inclusions:
- Banding patterns
- Moss-like dendritic inclusions (moss agate)
- Plume inclusions (plume agate)
localities:
- Brazil
- Uruguay
- India
- Madagascar
- USA
- Germany (Idar-Oberstein)
expressions:
- slug: massive
  name: Massive
  cdl: |
    #! Species: Chalcedony
    #! System: Trigonal (32)
    #! Habit: Massive cryptocrystalline
    amorphous[cryptocrystalline]:{massive}
  is_primary: true
  form_description: Chalcedony — cryptocrystalline variety of quartz composed of microscopic fibrous crystals. Encompasses many important gem varieties including agate, carnelian, chrysoprase, and onyx.
  forms:
  - massive
- slug: botryoidal
  name: Botryoidal
  cdl: |
    #! Species: Chalcedony
    #! System: Trigonal (32)
    #! Habit: Botryoidal grape-like form
    amorphous[cryptocrystalline]:{botryoidal}
  form_description: Botryoidal chalcedony forming grape-like rounded masses, typical of chalcedony deposits lining cavities.
  forms:
  - botryoidal