Cellulose.

That’s what I thought and was hoping

But probably uses asbestos as a binder.

God, I hate dealing with all the bullshit regulations we have to follow now.  If I have to hang something on the wall, it's cheaper to just pay the asbestos crew to come put a damned screw in the wall than it is to test the wall.  Problem is, fuckers don't know which end of a screwdriver to use.

Take a handful and use a lighter to scorch it.

While cellulose is 'flame retardant' an active flame from another source will char it.

If it is asbestos I probably have cancer now. I crawled around in that shit for hours yesterday changing a damn attic fan.

Likely ground to fine.

It cannot hold loft from its own weight.

FWIW this stuff won’t catch fire but it definitely scorches.

Fire is probably not a definitive test.

As I recall all that old stuff had some sort of fire retardant added to it, for obvious reasons.

Get a microscope.

Get a test kit.

I'm going to do a bit of research on this.

When was it put in?  If it was after 1990, it almost certainly contains no asbestos.  Prior to that it is a 'maybe'.

Taken from:  https://www.thespruce.com/how-to-identify-dangerous-asbestos-insulation-4119906

But asbestos can also be found in some types of loose-fill attic and wall insulation, too. You have no worries if your insulation is in batt form--the type of insulation that may pose a risk is ?loose-fill insulation that is poured loosely into joist or wall stud cavities. Beneath attic floorboards or inside walls, you may find many thousands of loose particles. That's the type of insulation that could pose a risk.

How, exactly, can you identify whether your attic insulation is asbestos? Let's look at the particulars of loose-fill insulation that may contain asbestos.

Vermiculite Attic Insulation

The main source of asbestos danger concerns vermiculite attic insulation, but not all brands or all sources of vermiculate pose a hazard. There is nothing inherently bad about vermiculite, which is a pellet-like mineral that expands at high temperatures and which is often used for gardening as an amendment that loosens soil and improves its ability to transmit water.

Vermiculite is also used for insulation, in particular the vermiculite that was mined by the Libby company in Montana for about 70 years, under the brand name Zonolite.

Zonolite presents a health danger only because it was contaminated with tremolite, an asbestos-like mineral. Even though the majority of U.S. vermiculite attic insulation did come from the Libby mine, keep in mind that about 30% did not come from this source.

Your Loose-Fill Insulation May Contain Asbestos If:
*  Your house was built before 1990.  Because the Libby mine closed in 1990, houses built or remodeled before that date might have asbestos-containing attic insulation. If it was built after 1990, the chances are reduced but not eliminated.
*  The insulation particles have a certain color.  Zonolite is usually gray-brown or silver-gold.
*  The particles have an accordion-like texture. Because Zonolite is subjected to heat, the accordion texture is a result of the particle puffing up.
*  If the insulation lays flat: Zonolite lays flat and firm in the joist cavity, as opposed to loose-fill fiberglass, which tends to fluff up, much like a snow drift.

Although Zonolite is a mineral, it is actually lightweight, because during the production process it is subjected to high heat that causes the particles to puff up.

Is the Loose-fill Gray, Soft and Without a Shine?

If so, it is probably cellulose insulation. Cellulose has a high recycled paper content, no minerals. Close examination will show that this puffy gray material does not contain earth minerals at all, but will look like shredded gray paper. Cellulose insulation is a perfectly safe type of insulation that is blown into the cavities between the joists.

Is the Loose-fill White and Fluffy, With a Little Shine?

If so, it is probably fiberglass fill. Because it is a glass product, fiberglass will have a slight shine when subjected to bright light. It is very soft, almost like cotton candy. Fiberglass can be a breathing nuisance, but it is not known to cause cancer.

Is the Loose-fill Gray, Puffy and Fibrous?

Another mineral-based loose fill insulation is rock wool, which frequently appears as bundles of fibers with a soft, cottony appearance. Rock wool is white, off white or brownish-white. Rock wool is a manufactured product, made by melting basaltic rock and dolomite and adding binders. The raw material is heated to 2,750 degrees Fahrenheit until it melts. The molten material is spun into fibers with air pressure. Rock wool is installed as loose insulation or as woven insulation batts, and like fiberglass, the insulation fibers should be handled with care, but are not known to cause cancer.

What if I Suspect I Have Zonolite Vermiculite Insulation?

If your loose-fill insulation fits the visual cues for vermiculite insulation, you can check to see if it is the asbestos-carrying Zonolite type by purchasing a DIY asbestos testing kit, or seeking a commercial firm who can test for asbestos. DIY kits are usually available for less than $50. If you discover that you do have insulation containing asbestos, you are well advised to seek an abatement company to handle its removal. Unfortunately, this is an expensive proposition, but you cannot place a price on your family's health.

It will char from an outside flame.
Asbestos does NOTHING.

Let's build on that.

Placed low in the flame (the blue part) cellulose will char (turn black) and start to glow.  The moving gas may blow away the ash as cinders but that is also definitive.

Asbestos will just get hot and glow.

You could have a mix of cellulose and asbestos, so you may see both effects.  If you burn it and still have a fibrous residue, you likely have asbestos, at least in part.

A microscope will almost certainly tell the tale, if you know what asbestos looks like (there are lots of photomicrographs online).

I was trying to think of a density test.  Asbestos should sink and cellulose float.  The thing is, although dense, the asbestos fibers are so small they may float due to the water's surface tension.  I just don't know.  Would a surfactant (detergent) in the water reduce the surface tension and allow this test to work.  I just don't know.

A microscope with polarized light is the definitive test used.

The asbestos panic was so bad for a while because the EPA decided NOT to bother explaining
there are multiple 'type' of asbestos and not ALL are dangerous.

The best understanding we have is that it appears to be the contaminants in 'brown' asbestos that are the actual hazard.
White asbestos is considered all that much a hazard.

Fiberglass brake pads are not a hazard.
Metalized fiberglass brake pads ARE.

The evaporated metal on the outside of the fibers makes the hazard.