I think "VC" might mean "very course." But either way, I think your stuff will work fine. Horticultural grade means safe for plant cultivation so that stuff is the right stuff. This is only my second year of SFG, so maybe someone more experienced can chime in if I'm wrong.

Here is a link that might be useful: Garden blog

Horticultural grade is good. Although, not necessary depending on the vermiculite manufacturer, the same exact contents may be packaged into different bags for different marketing/applications. My bags did not say the particle size either, so I looked up the manufacturer on the internet from the bag and called them to find out the size. For the manufacturer that distributes in this area, their horticultural grade comes in coarse & medium.

Thanks for the replies. I feel better. I might contact the manufacturer just out of curiousity.

Kim; From what I understand Horticultural grade = coarse and what Mel recommends in his book.That's what I used and it came from the local green house (what they use). Feeling better now?

Curt :-)

I do feel better now. Thank you!

Sorry, don't mean to be disagreeable, but our area horticultural vermiculite comes in medium & coarse ... http://palmettovermiculite.com/products.html

Although, I used medium last year and it was ok.

Not a problem for me angela. Thank you for clearing that up.

Curt :)

I was told to use stall refresher, it is the same as garden vermiculite & it is much cheaper.

Example:

https://www.tractorsupply.com/tsc/product/sweet-pdz-stall-refresher-25-lb-5065990?cm_mmc=feed--GoogleShopping--Product-_-5065990&gclid=Cj0KCQjwgtWDBhDZARIsADEKwgPZ-1a1V7OmY-D5XrU2Bx8ahlNnjnvFxhex

PDZ is zeolite. here is a paper stating the difference between it and vermiculite in garden soil. I use zeolite as litter box type material under my chicken coop roosts. It is compostable. I wouldn’t use it as a complete substitute for Vermiculite, but mixing some in to make the mix cheaper seems like a reasonable plan.

https://www.proquest.com/openview/bbb0b91b2038d1d595b59f35b6435184/1?pq-origsite=gscholar&cbl=2032440#:~:text=This%20means%20that%20zeolite%20is,micronutrient%20availability%20(especially%20Fe).