The dark gray-blue stone that splits into thin sheets along its natural cleavage. Roofs of every old New England town hall, slate-tiled patios, the chalkboards a generation actually learned cursive on, the Pennsylvania quarrymen's heritage product. Slate forms when mudstone gets squeezed sideways at low metamorphic temperature — the clay particles realign perpendicular to the squeeze, which is why a slate billet splits into thin parallel layers (the slate cleavage) rather than fracturing randomly. Welsh slate (Penrhyn) is the global reference for fine-grained roofing slate; Vermont and Pennsylvania slates are the American commercial canon. Buy from quarry direct (Camara Slate Vermont, Sheldon Slate, Penn Big Bed) or from architectural stone vendors like Stone Source.
Fine-grained foliated metamorphic rock, derived by low-grade regional metamorphism (~200–400 °C, low to moderate pressure) of pelitic protoliths (mudstones, shales). Mineralogy: quartz + muscovite (sericite) + chlorite + minor accessories (pyrite, hematite for color). Density 2700–2800 kg/m³. Compressive strength 100–200 MPa. Flexural strength 50–80 MPa across the cleavage, 70–110 MPa with the cleavage. Water absorption < 0.4 percent (the property that makes it weatherproof for roofing). Splits along the slate cleavage in thicknesses 3–12 mm typical for roofing tiles, 10–25 mm for paving, 20–40 mm for hearths. Cuts cleanly with a wet diamond saw or scoring + snapping along the cleavage with a slate hammer. Drills with masonry bits. Color range from deep blue-black (Welsh, Vermont semi-weathering) through gray (Pennsylvania) to green (Vermont unfading green) and purple (Welsh purple). The 'unfading' designations refer to color stability under UV and weather over decades — fading slates pick up rust streaks from oxidizing pyrite, which is desirable in rustic settings, undesirable on a dean's roof.
Principled BSDF defaults derived from the sphere matte finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material. Or grab the whole library at once: ForMaterials library →
# finish: matte albedo #3a4048 metallic 0.00 roughness 0.75 ior 1.45 transmission 0.00 clearcoat 0.00 sheen 0.00 anisotropic 0.00
{
"albedo": "#3a4048",
"metallic": 0.0,
"roughness": 0.75,
"ior": 1.45,
"transmission": 0.0,
"clearcoat": 0.0,
"sheen": 0.0,
"anisotropic": 0.0
}
# Blender 4.x — Principled BSDF
# Slate · finish: matte
import bpy
mat = bpy.data.materials.new(name="mat_slate")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value = (0.0423, 0.0513, 0.0648, 1.0)
bsdf.inputs["Metallic"].default_value = 0.000
bsdf.inputs["Roughness"].default_value = 0.750
bsdf.inputs["IOR"].default_value = 1.450
bsdf.inputs["Transmission Weight"].default_value = 0.000
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
# Slate · finish: matte
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_slate", materialType="Generic")
mat.setProperty("diffuse", (58, 64, 72)) # 8-bit sRGB
mat.setProperty("metallic", 0.000)
mat.setProperty("roughness", 0.750)
mat.setProperty("indexOfRefraction", 1.450)
mat.setProperty("transparency", 0.000)
mat.setProperty("coatingWeight", 0.000)
{
"_format": "Substance Designer / Painter \u2014 pbrMetalRough constants",
"_about": "Slate \u00b7 finish: matte",
"baseColor": {
"r": 0.0423,
"g": 0.0513,
"b": 0.0648
},
"metallic": 0.0,
"roughness": 0.75,
"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."
}{
"asset": {
"version": "2.0",
"generator": "ForMatter"
},
"materials": [
{
"name": "mat_slate",
"pbrMetallicRoughness": {
"baseColorFactor": [
0.0423,
0.0513,
0.0648,
1.0
],
"metallicFactor": 0.0,
"roughnessFactor": 0.75
},
"extensions": {
"KHR_materials_ior": {
"ior": 1.45
}
}
}
]
}# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Slate · finish: matte
def Material "mat_slate" {
token outputs:surface.connect = </mat_slate/PreviewSurface.outputs:surface>
def Shader "PreviewSurface" {
uniform token info:id = "UsdPreviewSurface"
color3f inputs:diffuseColor = (0.0423, 0.0513, 0.0648)
float inputs:metallic = 0.000
float inputs:roughness = 0.750
float inputs:ior = 1.450
float inputs:opacity = 1.000
float inputs:clearcoat = 0.000
token outputs:surface
}
}
ICOMOS-ISCS glossary; National Slate Association literature.
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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