Calcium nitrate is rarely sold in fine grain form because of how hygroscopic it is. It becomes soaking wet easily just leaving it out in the atmosphere. Having it in little ball form with a coating makes it much easier to work with, and it won't jam your spray systems. It's 100% water soluble.
Keep in mind that there are 2 common forms of calcium nitrate in use. The common 15.5-0-0 with 19% calcium is actually a double salt containing ammonium nitrate. This "greenhouse grade" calcium nitrate has the formula 5Ca(NO[SUB]3[/SUB])[SUB]2[/SUB].NH[SUB]4[/SUB]NO[SUB]3[/SUB][SUP].[/SUP]10H[SUB]2[/SUB]O
Pure calcium nitrate, which is more expensive and not commonly used for hydroponics, is 11.9-0-0 with 16.9% Ca. It has the formula Ca(NO[SUB]3[/SUB])[SUB]2[/SUB].4H[SUB]2[/SUB]O.
(you can check wikipedia for calcium nitrate "use as a fertilizer", or find the molar masses yourself and do the math to confirm the NPK and Ca.)
Keep in mind, these N P K ratings are percentages by mass. This means if 2 calcium nitrate products offer identical NPK, they are essentially the same purity product and can be used interchangeably.
I use Yara Calcium nitrate "greenhouse grade" which is the 15.5-0-0 19% Ca double salt. Got a 50lb bag of it a long time ago for 30 bucks and shipping. You can get 1 pound on cropking for like $2.90 USD if i remember correctly.
Well I will check it out but all i have seen in the past is field grade (good for lawns) and its usually coated
The jacks is 31.50 for 25 pounds though I will check it out bit. I do need pure grades since I run a high pressure spray system and also weigh my cal nitrate which is very hygroscopic and changes weight easily.