ForMatter/Materials/gemstone/Cubic Zirconia (CZ)
mat_gem_simulant_cubic_zirconia

Cubic Zirconia (CZ)

cubic zirconium dioxide (ZrO₂ stabilized with Y₂O₃ or CaO), diamond simulant · CZ, cubic zirconia, djevalite (historical)
highlast updated 2026-04-27
metallic 0.00
hue shift +0°

The diamond simulant the world settled on between 1976 and the rise of moissanite: cubic zirconia, ZrO₂ stabilized into the cubic crystal form that gives it the brilliance and dispersion that approximate (but don't reach) diamond. Cheap, optically vivid, hard but not diamond-hard, and identifiable from diamond by thermal-conductivity test. The mass-market "sparkle stone" of the late 20th century.

Cubic ZrO₂ stabilized with 8–18% Y₂O₃ or CaO (pure ZrO₂ is monoclinic at room temperature; the cubic form is stabilized by oxide doping). Skull-crucible grown by direct induction melting in a self-supporting frozen ZrO₂ shell. Mohs 8.0–8.5. Specific gravity 5.65–5.95 (heavier than diamond — diagnostic). Refractive index 2.15–2.18 (vs. diamond's 2.42). Dispersion 0.058–0.066 (higher than diamond's 0.044, which makes CZ "flashier" but visually less authoritative).

mechanical

  • mohs_hardness_range8.0–8.5
  • specific_gravity_range5.65–5.95
source: GIA; Wikipedia entry on cubic zirconia

optical

  • refractive_index_range2.15–2.18
  • dispersion_range0.058–0.066
source: GIA; Wikipedia

Sustainability

  • embodied carbon kg co2e per kg9
  • sourceEditorial estimate from ICE / Granta CES EduPack class databases — industry mean, with cradle-to-gate boundary unless otherwise noted. Embodied carbon for any specific product depends on supplier mix, recycled content, and energy grid; verify against a primary source before using these numbers in a sustainability claim.
  • recyclabilitymoderate — material is recyclable but secondhand market is thin
  • biodegradableFalse
visual
very bright, flashier dispersion than diamond, slightly less authoritative "life"
tactile
noticeably heavier than diamond at equivalent visual size — the easiest hand test

PBR starter values

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

# finish:      crystalline
albedo        #f8f8ff
metallic      0.00
roughness     0.05
ior           2.42
transmission  1.00
clearcoat     0.00
sheen         0.00
anisotropic   0.00
copy as JSON 
{
  "albedo": "#f8f8ff",
  "metallic": 0.0,
  "roughness": 0.05,
  "ior": 2.42,
  "transmission": 1.0,
  "clearcoat": 0.0,
  "sheen": 0.0,
  "anisotropic": 0.0
}
Blender 4.x Python 
# Blender 4.x — Principled BSDF
# Cubic Zirconia (CZ) · finish: crystalline
import bpy
mat = bpy.data.materials.new(name="mat_gem_simulant_cubic_zirconia")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value         = (0.9387, 0.9387, 1.0, 1.0)
bsdf.inputs["Metallic"].default_value           = 0.000
bsdf.inputs["Roughness"].default_value          = 0.050
bsdf.inputs["IOR"].default_value                = 2.420
bsdf.inputs["Transmission Weight"].default_value = 1.000
bsdf.inputs["Coat Weight"].default_value        = 0.000
bsdf.inputs["Sheen Weight"].default_value       = 0.000
bsdf.inputs["Anisotropic"].default_value        = 0.000
KeyShot Python (lux) 
# KeyShot 11+ — lux Python API, Generic material
# Cubic Zirconia (CZ) · finish: crystalline
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_gem_simulant_cubic_zirconia", materialType="Generic")
mat.setProperty("diffuse",      (248, 248, 255))   # 8-bit sRGB
mat.setProperty("metallic",     0.000)
mat.setProperty("roughness",    0.050)
mat.setProperty("indexOfRefraction", 2.420)
mat.setProperty("transparency", 1.000)
mat.setProperty("coatingWeight", 0.000)
Substance pbrMetalRough 
{
  "_format": "Substance Designer / Painter \u2014 pbrMetalRough constants",
  "_about": "Cubic Zirconia (CZ) \u00b7 finish: crystalline",
  "baseColor": {
    "r": 0.9387,
    "g": 0.9387,
    "b": 1.0
  },
  "metallic": 0.0,
  "roughness": 0.05,
  "ior": 2.42,
  "opacity": 0.0,
  "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_simulant_cubic_zirconia",
      "pbrMetallicRoughness": {
        "baseColorFactor": [
          0.9387,
          0.9387,
          1.0,
          1.0
        ],
        "metallicFactor": 0.0,
        "roughnessFactor": 0.05
      },
      "extensions": {
        "KHR_materials_ior": {
          "ior": 2.42
        },
        "KHR_materials_transmission": {
          "transmissionFactor": 1.0
        }
      }
    }
  ]
}
USD Preview Surface 
# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Cubic Zirconia (CZ) · finish: crystalline
def Material "mat_gem_simulant_cubic_zirconia" {
    token outputs:surface.connect = </mat_gem_simulant_cubic_zirconia/PreviewSurface.outputs:surface>

    def Shader "PreviewSurface" {
        uniform token info:id = "UsdPreviewSurface"
        color3f inputs:diffuseColor = (0.9387, 0.9387, 1.0)
        float   inputs:metallic     = 0.000
        float   inputs:roughness    = 0.050
        float   inputs:ior          = 2.420
        float   inputs:opacity      = 0.000
        float   inputs:clearcoat    = 0.000
        token   outputs:surface
    }
}
↓ download glTF material
Substitutes
Moissanite (Synthetic)
Lab-Grown Diamond (CVD)

Citations