Luxury fibres like cashmere or vicuna can make lovely, indulgent cloths for sports jackets.

Having mostly stuck to linen, tweed or related mixes in recent years, I recently commissioned a jacket in 100% cashmere (from Eduardo de Simone) and it’s striking how soft and sumptuous it felt.

I had forgotten what the softness was like, and how nice a partner the short-haired texture can be for denim.

And yet it’s also great for formal jackets. That recent commission was in a mid-brown herringbone, but I also have old cashmere jackets in navy (from Solito) and a pale-oatmeal colour (from Caliendo – all pictured below).

The navy cashmere appears very smart when worn with grey trousers, a white open-necked shirt and dark-brown shoes – and yet doesn’t feel too formal or old-fashioned.

The problem with cashmere, vicuna and similar fibres is that they don’t wear well. Being soft, they’re more likely to wear down at the elbows, or the cuffs.

These jackets are a luxury in that sense as well, therefore: something to commission when you already have a range of harder wearing jackets in the wardrobe.

There are ways to mitigate the fragility of cashmere, however.

You basically want a cloth that has more body, the most important factor of which is the yarn (its thickness and how it is spun).

However, the yarn is not something you can easily find out, so the best thing is to look for proxies – like the weight – and consider the weave.

The best lasting will be a twill rather than a hopsack or plain weave, and a weight of 340g/11oz or above.

I made the mistake of getting a lightweight cashmere with my navy Solito, which was only 9oz and has had heavy wear, leading to it balding a little on the elbows.

Still, there are always nice suede elbow patches, right?

(By the way, the weave makes less of a difference with overcoats, where a greater variety of weaves and yarns are used to achieve different effects.)

The softness of cashmere also makes it a poor choice for trousers, in general, and therefore for a suit.

Trousers in pure cashmere are likely to lose their crease, then their shape, and finally start bagging at the knees. Again, it’s a mistake I’ve made before: with a navy suit from Vergallo.

(If only this article existed six years ago!).

The only exception to this rule is worsted cashmere. Most cashmere cloths are woollens, because the fibres aren’t long enough to make into a worsted yarn. But by selecting only the longest fibres, it is possible to make one.

The problem is this makes the cloth more expensive, as it’s a further refinement of an already rare fibre. And a worsted cloth doesn’t necessarily have the softness you’d expect from a cashmere.

When it comes to qualities of cashmere, there is a big range, with the best coming from Mongolia and cheaper versions coming from the rest of China, Iran or Afghanistan.

But it’s very hard to tell them apart when selecting cloth, and in any case the ones used by the big mills don’t vary much. It’s just perhaps best to avoid precious fibres from unknown mills or merchants.

The biggest problem with cheap cashmere, by the way, is the mix of fibre lengths, which is what causes pilling. If you see a friend with a cashmere jacket that has pilled heavily, you know to avoid the cloth.

Other precious fibres like vicuna are so rare, and the supply so restricted, that there aren’t the same problems with quality.

The only slight variation in vicuna is colour. The majority is caramel brown, and can therefore only be dyed darker colours than that. Much rarer is white vicuna, which can be dyed lighter colours.

Other precious fibres include camelids like guanaco or alpaca. These are rarely used in menswear, and when they are it’s usually in a mix with merino.

The finer types of alpaca approach vicuna in softness, however, and share the same properties of tensile strength and thermodynamic performance (retaining warmth).

These include Sury (a rarer breed), Baby (an animal less than a year old, like baby cashmere) and Royal (the finest – baby alpaca with coarser hairs removed).

Cashmere jackets can be wonderful, but they do need looking after. 

Brushing a cashmere jacket or overcoat is particularly useful, as it serves to separate those short, soft hairs. Worth doing regularly.

As to wool/cashmere mixes, the reason the cashmere is there is to make the cloth feel softer: some manufacturers will put a little cashmere in the mix to disguise fairly coarse wool elsewhere.

So my advice is to feel it and see if it’s actually softer than a nice 100% wool, rather than just assuming it is.