Lens material: "glass" vs. "crystal"

In my quest for better understanding the various products in the world of optics,
I've started to read a little about actual lenses, the heart of scopes/binos.

I don't have a full understanding yet, but, is it not correct to say that you could
form two fundamental categories of products, those with glass lenses
and those with crystal lenses ?

Glass is not crystal. The phrase "crystal clear" does have meaning.

I do know that it's more complex than just "crystal", there are many different
kinds of crystalline materials and lattice structures. But, fundamentally, there's
crystal and there's non-crystal. (Not even discussing lens coatings !)

So next, I want to find out which manufacturers, or products, use glass lenses
and who uses crystal. I'm fairly sure Swarovski uses crystal, and Meopta also.
How about Leupold and Nightforce ? I'm also told that Vortex is definitely not crystal.

Please chime in if you any info or insights !

I'm really curious about the ultra high-end stuff, Kahles/USO/Marsh/Steiner/Hensoldt/etc.

Growing and grinding a lens the size of a typical scope objective or ocular diameter out of a single true crystal would be insanely expensive. I say there are no such consumer grade rifle scopes or binoculars on the market at this time, and won't be anytime soon.

Maybe there is some misunderstanding in what is meant by "crystal" in this context? In other words, what the marketing folks at Swarovski mean when they say "crystal" has no relation to what an optical engineer means when he says the same word.

Interesting, flourite has been in use optically since 1986. There are a few companies that talk about pure flourite objectives. Kowa for example.

False claims, or am I misunderstanding?

The swarovski lenses in sureloc sights are awesome for clarity.

Not sure about correcting for your prescription, they are fuzzy for people who don't use a small peep and a clarifier depending on your eye.

When Swarovski marketing materials mentions a "crystal" decanter or a "crystal" wine goblet, the last thing they are thinking about is that item being made from a true single crystal.

It is true that Canon made/makes some high end camera lenses that utilize one or two fluorite elements in it to reduce chromatic dispersion. But, that is quite different from an entire lens assembly made up of single crystal elements. Plus, fluorite was the only crystal ever used as such, the oddball rare exceptions notwithstanding. Fluorite is relatively fragile, and so would be problematic in a rifle scope expected to withstand recoil and field abuse. And, fluorite elements are even less common, now, due to there being cheaper ways to achieve a similar reduction in chromatic aberrations, such as ultra low dispersion glass, which is an amorphous glass rather than a true single crystal component.

To the OP's question: "is it not correct to say that you could
form two fundamental categories of products, those with glass lenses
and those with crystal lenses"? IMHO, for rifle scope and binoculars, the answer is "no" because there are no scopes or binos made of true single crystal optical elements.

JMHO

Shinbone, Thanks for your insight. It's entirely possible that I need to do more reading
on this.
I would ask, What then does Swarovski mean when they refer to "crystal" ?

It's easy to see that a 50mm clear diamond lens would be rather pricey. But I thought
that crystal structures made from other materials had become much more commonplace in the last 30 years or so. Watchglass sapphire "crystal" covers, for
example, or smartphone screen covers.

As used by Swarovski (and other manufacturers), "crystal" is an industry name for leaded glass, which is glass with a high lead content making it decorative.

https://en.wikipedia.org/wiki/Lead_glass

Swarovski scopes use Schott glass afaik (Schott AG is owned by the same consortium as Zeiss). Nobody uses flourite in riflescopes that I know of. Some have mentioned its use in spotting scopes and camera lenses. Flourite is also used in some specialty camera lenses for its transmissivity in non-visible wavelengths (UV/IR lenses), this feature provides no benefit for an optical wavelength system.

I may be barking up the wrong tree with this idea.

So, everyone uses quality glass, of some sort, some
glass evidently optically (or otherwise) better than others.
This is not news, just my understanding. No true crystal.