ForMatter/Materials/gemstone/White Opal (Australian)
mat_gem_opal_white_australian

White Opal (Australian)

opal (hydrated SiO₂·nH₂O), play-of-color, light body tone · light opal, milky opal, Coober Pedy opal
highlast updated 2026-04-27
metallic 0.00
hue shift +0°

Hydrated silica that diffracts light through a regular array of submicron silica spheres — the rainbow you see flashing inside an opal isn't pigment, it's structural color, the same physics that paints a peacock feather. White opal has a pale milky body; the play-of-color floats inside like fish in clear water. Australia produces about 95% of the world's precious opal, with white opal coming mostly from South Australia.

Amorphous hydrated silica (SiO₂·nH₂O, n=3–10%). Mohs 5.5–6.5. Specific gravity 2.10. Play-of-color from Bragg-style diffraction off close-packed silica spheres (~150–400 nm diameter) in the gem; sphere size determines visible-spectrum range of the play. Sensitive to dehydration cracking ("crazing") if exposed to dry / hot environments — never store with desiccants, never ultrasonic-clean.

mechanical

  • mohs_hardness6
  • specific_gravity2.1
  • water_content_pct6
source: GIA Opal Quality Factors

optical

  • refractive_index1.45
source: GIA

Sustainability

  • embodied carbon kg co2e per carat0.7
  • recyclabilitymoderate — secondhand market exists but stones are fragile in re-setting
  • biodegradableFalse
  • localityprimary mining: Australia (Coober Pedy, Andamooka, White Cliffs)
visual
milky pale body with vivid play-of-color flashes (red, orange, green, blue)
tactile
warmer to the touch than other gemstones — silica + water + low density

PBR starter values

Principled BSDF defaults derived from the sphere iridescent finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material.

# finish:      iridescent
albedo        #e8e8f0
metallic      0.70
roughness     0.30
ior           1.45
transmission  0.00
clearcoat     0.50
sheen         0.50
anisotropic   0.00
copy as JSON 
{
  "albedo": "#e8e8f0",
  "metallic": 0.7,
  "roughness": 0.3,
  "ior": 1.45,
  "transmission": 0.0,
  "clearcoat": 0.5,
  "sheen": 0.5,
  "anisotropic": 0.0
}
Blender 4.x Python 
# Blender 4.x — Principled BSDF
# White Opal (Australian) · finish: iridescent
import bpy
mat = bpy.data.materials.new(name="mat_gem_opal_white_australian")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value         = (0.807, 0.807, 0.8714, 1.0)
bsdf.inputs["Metallic"].default_value           = 0.700
bsdf.inputs["Roughness"].default_value          = 0.300
bsdf.inputs["IOR"].default_value                = 1.450
bsdf.inputs["Transmission Weight"].default_value = 0.000
bsdf.inputs["Coat Weight"].default_value        = 0.500
bsdf.inputs["Sheen Weight"].default_value       = 0.500
bsdf.inputs["Anisotropic"].default_value        = 0.000
KeyShot Python (lux) 
# KeyShot 11+ — lux Python API, Generic material
# White Opal (Australian) · finish: iridescent
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_gem_opal_white_australian", materialType="Generic")
mat.setProperty("diffuse",      (232, 232, 240))   # 8-bit sRGB
mat.setProperty("metallic",     0.700)
mat.setProperty("roughness",    0.300)
mat.setProperty("indexOfRefraction", 1.450)
mat.setProperty("transparency", 0.000)
mat.setProperty("coatingWeight", 0.500)
Substance pbrMetalRough 
{
  "_format": "Substance Designer / Painter \u2014 pbrMetalRough constants",
  "_about": "White Opal (Australian) \u00b7 finish: iridescent",
  "baseColor": {
    "r": 0.807,
    "g": 0.807,
    "b": 0.8714
  },
  "metallic": 0.7,
  "roughness": 0.3,
  "ior": 1.45,
  "opacity": 1.0,
  "anisotropyLevel": 0.0,
  "_notes": "Channels listed are the standard Substance pbrMetalRough output. Drop into a Uniform Color node per channel, or as the constant input on a layered stack."
}
glTF 2.0 Metallic-Roughness 
{
  "asset": {
    "version": "2.0",
    "generator": "ForMatter"
  },
  "materials": [
    {
      "name": "mat_gem_opal_white_australian",
      "pbrMetallicRoughness": {
        "baseColorFactor": [
          0.807,
          0.807,
          0.8714,
          1.0
        ],
        "metallicFactor": 0.7,
        "roughnessFactor": 0.3
      },
      "extensions": {
        "KHR_materials_ior": {
          "ior": 1.45
        },
        "KHR_materials_clearcoat": {
          "clearcoatFactor": 0.5
        },
        "KHR_materials_sheen": {
          "sheenColorFactor": [
            1.0,
            1.0,
            1.0
          ],
          "sheenRoughnessFactor": 0.5
        }
      }
    }
  ]
}
USD Preview Surface 
# USD Preview Surface — UsdShade.MaterialLook prim attributes
# White Opal (Australian) · finish: iridescent
def Material "mat_gem_opal_white_australian" {
    token outputs:surface.connect = </mat_gem_opal_white_australian/PreviewSurface.outputs:surface>

    def Shader "PreviewSurface" {
        uniform token info:id = "UsdPreviewSurface"
        color3f inputs:diffuseColor = (0.807, 0.807, 0.8714)
        float   inputs:metallic     = 0.700
        float   inputs:roughness    = 0.300
        float   inputs:ior          = 1.450
        float   inputs:opacity      = 1.000
        float   inputs:clearcoat    = 0.500
        token   outputs:surface
    }
}
↓ download glTF material
Substitutes
Black Opal (Lightning Ridge)

Citations