Lizardite - www.Crystals.eu

Lizardite

Lizardite • Serpentine group (phyllosilicate) Formula: Mg3Si2O5(OH)4 (± minor Fe, Ni, Al) Crystal system: Trigonal polytype (1T/2H) • Platy habit Mohs ~2.5–3.5 • SG ~2.55–2.62 Luster: Greasy–waxy • Cleavage: Perfect basal

Lizardite — The Platy, Pastel Face of Serpentine

Lizardite is the soft‑green, sheet‑structured member of the serpentine family—the calm cousin to fibrous chrysotile and wavy antigorite. It forms when ultramafic rocks (think peridotite and dunite) meet water and transform, layer by layer, into silky, waxy, greenstone. Under a hand lens, lizardite looks like tiny overlapping plates; underfoot, it often builds whole hills of serpentinite. It’s geology’s version of a spa day: hot olivine, lots of water, and a complete mineral makeover.

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Structure
T‑O‑T sheets (talc‑like) + brucite‑like layer → flat plates
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Often Magnetic?
Serpentinization makes magnetite grains → weak magnet pull
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Lives In
Serpentinite, mesh textures after olivine, bastite after pyroxene

Identity & Naming 🔎

Serpentine family portrait

Lizardite belongs to the serpentine group alongside antigorite (corrugated sheets) and chrysotile (rolled sheets → fibers). Lizardite’s sheets stay flat, assembling into platy, pseudo‑hexagonal microcrystals that pack into smooth masses.

Name & place

Named for the Lizard Peninsula in Cornwall, UK, where classic serpentinites crop out. If the name made you picture tiny reptiles—same here. Alas, no actual lizards were consulted.

Terminology tip: “Serpentine” is the mineral group; serpentinite is the rock made mostly of serpentine (often lizardite‑rich) with magnetite and friends.

Formation & Geological Setting 🌍

Hydration of ultramafics

Lizardite forms during serpentinization—the reaction of olivine and pyroxene with water at low to moderate temperatures. Hydrogen moves in, silica reorganizes, and Fe partly oxidizes to magnetite. Volume expands, rock weakens, and new micro‑fractures invite more fluid—a self‑feeding makeover.

Where it happens

At mid‑ocean ridges, in ophiolite belts uplifted onto continents (Oman, New Caledonia, California Coast Ranges), and in subduction mélange zones. Near the surface, weathering softens serpentinite into green soils rich in Ni/Cr.

Team serpentine

Lizardite dominates at lower temperatures; with more heat, structures reorganize toward antigorite. Chrysotile develops where rolling the sheets relieves stress along veins—think scrolls (chrysotile) vs. pages (lizardite).

Recipe card: peridotite + water + time → lizardite + magnetite + heat of hydration (it even makes the rock warm as it forms!).

Colors & Textures 🎨

Palette

  • Pale apple to mint green — classic massive lizardite.
  • Yellow‑green — Fe‑rich zones.
  • Soft jade‑like green — when mixed with fine magnetite/chorite.
  • Grey — silica‑rich or weathered surfaces.
  • Brown veining — iron oxide staining.

Luster ranges from waxy to greasy. Fresh breaks can look slightly soapy, but don’t be fooled—talc (the truly soapy one) is softer.

Textures you’ll meet

  • Mesh serpentine — honeycomb pattern pseudomorphing olivine grains; magnetite lines the meshes.
  • Bastite — felted platiness replacing pyroxene crystals, leaving rectangular ghosts in the rock.
  • Vein serpentine — pale green lizardite along micro‑cracks, sometimes bordered by chrysotile fibers.

Photo tip: Side‑light at ~30° pops the mesh/bastite ghosts; a white bounce card keeps greens natural.

Physical & Optical Properties 🧪

Property Typical Range / Note
Chemistry Mg3Si2O5(OH)4, with Fe/Ni/Al substitutions common
Crystal system Trigonal polytypes (1T, 2H); forms platy microcrystals
Hardness ~2.5–3.5 (soft; scratches with steel)
Specific gravity ~2.55–2.62
Cleavage / Tenacity Perfect basal cleavage; sectile; plates flexible in thin leaves
Luster / Streak Waxy to greasy; streak white
Refractive indices n ~1.53–1.57 (low); birefringence weak to moderate
Pleochroism None to very weak (pale green tints)
Magnetism Weak attraction common due to magnetite from serpentinization
Optical shorthand: Low relief, low‑order interference colors, and sheety extinction—lizardite is the mellow one under the microscope.

Under the Loupe / Microscope 🔬

Platy mosaic

At 10×, look for a mosaic of tiny plates reflecting at slightly different angles—like stacked fish scales. Cleavage is subtle but gives a satin sheen when rocked under light.

Mesh & bastite clues

Mesh texture appears as polygonal patches with dark seams; bastite looks like rectangular patches where pyroxene once stood—both classic footprints of serpentinization.

Accessory grains

Tiny magnetite specks (test with a magnet), brucite plates, and occasional chromite are common companions in serpentinite.

Look‑Alikes & How to Tell 🕵️

Talc

Softer (Mohs 1), unmistakably soapy feel, often lighter green/white. Talc doesn’t show the serpentine mesh/bastite ghosts.

Jade (nephrite)

Tough, felted amphibole aggregate with splintery fracture and higher hardness (~6–6.5). Serpentine sold as “new jade” is softer and waxier.

Chrysotile (serpentine asbestos)

True fibrous habit and silky luster in veins. Lizardite is platy, not thread‑like; most carvings/slabs are lizardite‑rich, not chrysotile.

Antigorite

Often darker, with bladed to corrugated textures and higher thermal stability. Thin sections show more pronounced undulations in layers.

Dyed composites

Unnaturally uniform neon greens and color pooling in pores are red flags. Natural lizardite shows subtle mottling and mineral specks.

Quick checklist

  • Waxy/greasy luster; soft (2.5–3.5).
  • Platy micro‑mosaic; mesh/bastite textures common.
  • Often weakly magnetic (magnetite specks).

Localities & Associations 📍

Classic belts

Cornwall (UK)—type area; Oman ophiolite; New Caledonia (nickel laterites on serpentinite); Italy (Apennines); Quebec & Newfoundland; California Coast Ranges. If the map shows an ophiolite, odds are good for lizardite.

Mineral neighbors

Magnetite, brucite, chromite, talc, chlorite, and occasionally native Ni‑Fe alloys in highly reduced pockets. In veins, chrysotile and carbonates may appear.

Care, Handling & Display 🧼

Everyday handling

  • Softness alert: Avoid sharp knocks and abrasion; edges bruise easily.
  • Great for carvings and beads; rings need protective settings due to wear.

Cleaning

  • Lukewarm water + mild soap + soft cloth; rinse and dry.
  • Avoid harsh acids/alkalis and ultrasonic/steam—micro‑fractures don’t love them.

Display & storage

  • Store away from harder quartz/corundum pieces.
  • Side‑lighting around 30° makes the waxy sheen glow and reveals mesh textures.
Lapidary aside: Use light pressure, fresh abrasives, and coolants. Cerium or alumina on a soft pad gives a gentle sheen—let the polish glide, not grind.

Questions ❓

Is lizardite the “asbestos” serpentine?
No—the fibrous serpentine is chrysotile. Lizardite is typically platy and massive, common in carvings and slabs.

Why is my serpentinite weakly magnetic?
Serpentinization produces tiny magnetite grains; a small magnet often feels a gentle tug.

What’s “new jade” in the trade?
Often light‑green serpentine (frequently lizardite‑rich), not true jade. It’s softer and waxier than nephrite/jadeite.

Can lizardite be translucent?
Thin slices can show a soft green translucency, but most pieces are opaque with a warm, waxy glow.

Any fun field clue?
Green, slick serpentinite with honeycomb “mesh” under a loupe + weak magnetism = you’re probably meeting lizardite. Bonus: slickensides (polished fault surfaces) are common, and very photogenic.

Small joke to close: lizardite doesn’t bask on rocks—it is the rock doing the basking.
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