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).
Principled BSDF defaults derived from the sphere crystalline finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material. Or grab the whole library at once: ForMaterials library →
# 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 thickness 0.80 attenuation_distance 1.50
{
"albedo": "#f8f8ff",
"metallic": 0.0,
"roughness": 0.05,
"ior": 2.42,
"transmission": 1.0,
"clearcoat": 0.0,
"sheen": 0.0,
"anisotropic": 0.0,
"thickness": 0.8,
"attenuation_distance": 1.5
}
# 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 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)
{
"_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."
}{
"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 — 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
}
}
ICA International Colored Gemstone Association; GIA CZ identification.
House vocabulary — terms ForMatter uses with intent.
Materials and processes for people who design and make things.
A local-first library of materials, processes, applications, and finishes — equal weight, citable everywhere, with cost-over-volume curves, trade-off profiles, equipment-tier filters, and second-life paths layered onto the data so a student can move from "what is this" toward "what's actually buildable here, now, by me." Part of the renato.design ecosystem — sibling of Plenum, Specimen, Ingenue, gesture, graf, and the Renato Rhino plug-ins. Form and matter, inseparable.
Half of teaching materials is teaching how the material is made into the thing. The standard subscription library was always light on that half. The wedge here isn't better samples or a prettier interface — it's treating Process as a peer entity, not a footnote.
Conway's Material World on raw materials, Lefteri's Making It on processes, Forty's Concrete and Culture, Sparke's Design in Context, Bürdek's Design: History, Theory and Practice of Product Design, Schröpfer's Material Design on materials in architecture, Winchester's The Perfectionists on tolerance, Minshall's Your Life Is Manufactured on the global supply chain, von Busch's Making Trouble on material activism, Were's How Materials Matter, Hegger / Drexler / Zeumer's Basics Materials, Untracht and McCreight on metalsmithing, USDA Forest Products Lab on woods, GIA on gemstones, Schott / CoorsTek / Toray / Owens Corning datasheets, MakeItFrom for verifiable property numbers, ASM Handbook, ISO standards. Museum holdings draw from the Met, MAD, V&A, Smithsonian American Art Museum, Newark Museum of Art, British Museum, Heard Museum, Smithsonian NMAI, Eiteljorg Museum, Philadelphia Museum of Art, Cranbrook Art Museum, and Grand Rapids Art Museum — collection-record permalinks only, designer overview pages and exhibition listings excluded. Voice blocks now ride on every entry kind — material, process, application, and finish — and include Ruskin on iron, Anni Albers on twining, Greg Lynn on the shred-and-teeth NURBS lineage, Pugin on the metal that won't be hammered, Barthes / Yanagi / Benjamin channeled within their philosophy; Sparke, Bürdek, Forty, Conway, Schröpfer, Minshall, von Busch, Lefteri, Pat Pruitt, Mary Lee Hu, Tom Joyce, Albert Paley, and the rest of the contemporary makers quoted verbatim with citation. All cited.
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