Minden Ore Goo - Loki Smelt

Marcus was able to run a sample of the Minden 'Iron Goo' ore through his testing. This gives us the values bellow, along with his comments.

As a background here, the source material was gathered at a roadside ditch just south of Minden Ontario in the spring of 2006. David Robertson and I had discovered the deposit quite by accident on a trip up to the area. A rock cut along the road contained a layer that was an iron ore deposit. Some of the rock was gathered, but it proved to be only a small amount of iron oxide layered in with a course sand and compressed into a sandstone like material. When this material was roasted, it became only slightly magnetic - which I took to mean only a small amount of iron was actually present.
I was hopefull that the presence of even some iron in the rocks might lead to a bog ore deposit close by. The contour of the land is such that the drainage from the rock cut runs down about 100 meters to a low bog. On a second trip to the site, I did examine the bog itself, but although some of the surface signs for bog ore existed, I did not find a deposit of primary bog ore.
What I did find was a particular material throughout the drainage ditch along the base of the rock cut. This was a redish brown colour, and about the consistancy of chocolate pudding, that layed in a loose layer just at the bottom of the water in the ditch. It could be gathered by straining it out through your fingers. Over roughly two and half hours I pulled out enough of this material to fill about five standard 5 gallon plastic pails. As you might guess this incuded a lot of water.
Over the next several months, I allowed the pails to dry in the sun, eventually rendering down the material to a dry clay like consistancy yielding 22 pounds (10 KG) total.

Showing the ore source

This is 'just barely' enough ore material to undertake a smelt. Most definately the relative iron content becomes very important in determining this. The DARC smelt series points to a threshhold amount or ore required - which also relates to the smelter size. Given our own use of a relatively standard size at roughly 25 cm diameter (10 inches), we have consistantly found that we need at least 8 - 10 kg of ore to get the correct formation of a slag bowl and what I'm going to call a 'seed bloom'. This using the Virigina Rock Ore sourced by Lee and Skip, which is in the 60 % iron oxide range. Ore addtions OVER that amount just appear to increase the overall size and density of the bloom being created. (Note that this is at best a rough rule of thumb - I'd be happy to hear from those experimenters who have gotten different and better results!)

For those of you who attended Early Iron 3 this year, the demonstration smelt I carried out on Saturday used the Minden Iron Goo as the ore material. The 'Loki' smelter was somewhat reduced in diameter - to roughly 20 cm / 8 inches. Detailed notes on the conduct of the smelt can be found at:
www.warehamforge.ca/ironsmelting/Early Iron 03/LOKI-EI3.html
And also on the BLOG at the posts:
Friday, October 20, 2006
'Loki' Smelter - part 2
Thursday, October 19, 2006
'Loki' Smelter at Early Iron

SO - to the POINT

Skip had commented at the time when the smelter was pulled apart that he wondered about a possible high silica content to the starting ore material. He remarked how the slag was much more glassy than what is normally seen - almost like a poor quality soda glass. This observation is borne out by the content of the ore sample - with about 18% silicon dioxide present. The relative iron content of the ore is also certainly on the low end - at only 42 %.
If you extract the volatile elements (as Marcus comments on) the starting ore is closer to 60 % iron oxide. Note that the ore was NOT roasted before it was added, which of course we would normally do. In this case this initial step was not undertaken because of the powdery quality of the material. Although roasting would have increased the relative purity of the ore, it also means that the total effective amount of iron ore added to the smelt was closer to 6.3 KG / 14 lbs total. This is again under what we are finding as our minimum threshold.

The Loki smelt did produce some metallic iron. There was only a small amount, about .68 kg / 1.5 lbs. This was mainly in the form of some small fingers of high carbon cast iron, plus a number of small oval shaped balls of similar material spread through the glass slag. If the effective ore amount is considered to be that 6.3 kg / 14 lbs however, this means a return of ore to iron at about 9 %.

One obvious concern is the smaller particle size for this ore material. I think this is primarily responsible for the high carbon content of the metal produced. Higher additions of ore to charcoal might correct for this. Without a doubt, considerably more of this specific ore needs to be used if any useful result is expected.

Yet ANOTHER series of experiments to add to the list!

Darrell

****************************
Tuesday November 28

Hi Darrell,

On Friday, I got back the data for the sample of the Minden goo that you
gave me. I have reproduced it below. Looking at the data, the high loss
on ignition value (LOI) shows that there are a lot of volatile
components there. This is most likely structurally bound water, but may
include some carbon dioxide from decomposition of carbonates. I did not
request total carbon analysis, so have do not have the information with
which to comment on this. If all these volatiles can be removed by
roasting prior to smelting, then the ore could produce an initial
material that is ~61 wt% Fe2O3. If not, then a lot of the weight that
goes into the smelter will not be iron and will be driven off at an
early stage of smeltin (taking heat to do it). Although the volatile
content of the ore is similar to that which you gave me from LAM, it is
much more silica rich, so has an overall lower Fe content (42 vs. 66 wt%
Fe2O3). Full analyses of the LAM material are on the web site. If you
have any questions about these data, let me know.

Regards,

Marcus.

*Sample ID* 06-0356-0001
Client ID Det Limit MIN01 Volatile-free
units wt% wt% wt%
SiO2 0.01 17.88 25.67
*TiO2* 0.01 0.13 0.19
*Al2O3* 0.01 3.11 4.46
*Fe2O3T* 0.01 42.4 60.87
*MnO* 0.01 0.42 0.60
*MgO* 0.01 0.61 0.88
*CaO* 0.01 3.55 5.10
*Na2O* 0.01 0.78 1.12
*K2O* 0.01 0.71 1.02
*P2O5* 0.01 0.07 0.10
*LOI* 0.05 29.61
*TOTAL* 99.26

Fe2O3T = total Fe expressed as Fe2O3