Cashmere vs Merino vs Alpaca vs Vicuña A Comparison Guide to Luxury Knitwear Fibres

Every luxury knitwear house has a fibre it is known for — Loro Piana and vicuña, John Smedley and merino, Kuna and alpaca — and every fibre has its own logic of fineness, warmth, durability and price. This guide compares the ten fibres that appear in the index so you can choose the right one for the garment you want, rather than defaulting to cashmere because it is the most famous.

The comparison at a glance

Fineness is what you feel

Softness has a physical explanation. Human skin registers a fibre as "prickly" when its diameter exceeds roughly 28–30 µm, because a thick fibre resists bending and pokes rather than folds. Below about 19 µm almost no one feels prickle; below 15 µm the fibre feels like nothing at all. That is why vicuña and Grade A cashmere are in a class of their own, why extra-fine merino (under 18.5 µm) is comfortable next to the skin while ordinary merino is not, and why Shetland wool, at 23–30 µm, is meant to be worn over a shirt.

Warmth is about trapped air

A fibre insulates by trapping air. Fine, crimped fibres trap the most, which is why cashmere is commonly cited as seven to eight times warmer than sheep's wool by weight. Alpaca and yak have a partly hollow fibre structure that adds insulation, making them warmer than merino and close to cashmere. Mohair is warm because its halo of loose fibres holds a layer of air around the fabric. Merino's virtue is not maximum warmth but regulation: it absorbs and releases moisture, so it stays comfortable across a wide range of temperatures.

Durability is about length and strength

Long, strong fibres resist pilling and abrasion. Worsted-spun merino, with its long parallel staple, is the most durable of the fine fibres; alpaca's long fibre and yak's natural strength follow. Cashmere is the exception among luxury fibres: it is soft precisely because it is fine and short-ish, and it will always pill more than merino or alpaca of comparable quality. Lambswool and Shetland are coarser but exceptionally hard-wearing; a Shetland crew neck from a Scottish mill routinely lasts twenty years.

Each fibre in brief

Cashmere

The benchmark luxury fibre. Grade A (under 15.5 µm, long staple) from Inner Mongolia and Mongolia, knitted in Scotland or Italy, is the reference sweater. Its weaknesses are pilling and price; its strength is a softness and warmth nothing else at its price matches. Read the grading guide.

Merino

The workhorse of fine knitwear. Extra-fine merino knitted at 21–30 gauge — the English fine-gauge tradition — is a genuine luxury product that travels, washes and lasts better than cashmere. At ordinary grades and gauges it is a commodity.

Alpaca

Peru's fibre. Royal alpaca (under 19 µm) rivals cashmere for softness with more lustre and far better durability; baby alpaca (19–22.5 µm) is the mainstream luxury grade. It contains no lanolin, so it suits sensitive skin. Its drawback is a lack of elasticity, which is why it is often blended with silk or merino.

Vicuña

The rarest fibre on earth, from a wild, protected Andean camelid shorn every two to three years. At 12–13 µm it is finer than anything else, usually left undyed in its natural cinnamon shade, and priced accordingly. Loro Piana dominates the supply.

Yak down

The sustainable cashmere alternative from the Tibetan plateau and Mongolia: 16–19 µm, naturally brown or grey, warmer than merino, more durable than cashmere, with a drier hand. Increasingly used by slow-fashion knitwear houses.

Baby camel

Bactrian camel down from the Gobi, 16–19 µm and naturally golden. Rare in knitwear, prized for cashmere-like softness with better shape retention.

Lambswool and Shetland

The classic British fibres. Geelong lambswool (around 19–20 µm) from a Scottish mill is remarkably soft; Shetland is lofty and rustic and softens with washing. Both are affordable, warm and last decades.

Mohair

Kid mohair from the Angora goat, usually blended with silk, gives a light, luminous, fuzzy sweater. Adult mohair is coarse and belongs in outerwear.

Silk blends

Silk is rarely knitted alone but transforms cashmere and cotton: cashmere-silk is lighter, cooler and more lustrous than pure cashmere, and holds its shape better — the summer-weight luxury knit.

Sea Island cotton

Extra-long-staple cotton from the West Indies, knitted at 30 gauge, produces a polo shirt with the hand of silk. Egyptian Giza and Peruvian Pima are the close relatives.

Choosing by garment

• A winter crew neck for cold climates: 2-ply Scottish cashmere, or 4-ply for real cold; yak or baby camel for a sustainable alternative.
• An everyday layering sweater: extra-fine merino at 18–24 gauge.
• A polo shirt or summer knit: Sea Island cotton or cashmere-silk.
• A sweater that must last: royal alpaca, worsted merino or Scottish lambswool.
• The most luxurious object you can buy: vicuña, or baby cashmere from a Scottish or Italian house.
• Sensitive skin: royal or baby alpaca.