Sorry to high-jack this thread, but this is important:
Laguna Borate is their manufactured sub for gerstley borate : absolutely , 100% no doubt
See the Laguna catalog !!!!!! : http://www.lagunacla.../lcc_dryraw.pdf
Look at the list of materials there: it clearly says for Laguna borate:
A specially formulated flux containing a high percentage of boron. This material mimics the fluxing characteristics of Gerstley Borate: "
and even in the link you sent http://digitalfire.c...gunaborate.html : if you read it it is quite clear that it is what I am saying:
Laguna Borate Laguna Clay claims this is almost identical in every glaze they have tried and is less expensive than Gerstley Borate was.."
"Laguna Borate has the distinction of being the least expensive substitute available. "
Yes, the remaining stocks of of Gerstley are owned by Laguna: it is still sold by them and others as Gerstley Borate.
The link you posted for the Gerstley B chem analysis is for of the remaining stuff that came from the mine: (in it they claim that is consistent, but we all know it's not very consistent)
The stuff that is consistent is the manufactured versions ! Laguna started making the sub when everyone else did ... they then bought the remaining stocks of the natural stuff as well.
On Tony Hansens page (http://digitalfire.c...ubstitutes.html) he shows the chem analysis of the manufactured subs, including Laguna Borate, vs the actual mined stuff.
So Norm, if you have been ordering "Laguna Borate" from them, you are using the consistent manufactured sub,
if you have been ordering "Gerstley borate" from Laguna then you are using the stuff from the mine.
Both products say laguna on the bag: both are available, but are not the same material.
Yes, it is a bit confusing,that's why it's important that people get the difference here, especially since so many people love the floating blue glazes!
The long and short of it is : if you can buy the original mined GB, don't do it. Get one of the substitutes like Laguna B or Gillespie B: they do what you need and are the same bag to bag.