Sandra - has a driller knocked you up?

Are you pregnant? Cuz you're late

• 166 days - 5 and a half months since you awarded the contract for the 43-101 calculation (link)
• 121 days - 4 months since you teased us in a PR about metallurgical studies (link)

I'm sure that there is nothing to worry about, let us check out REX.V!

ohh, nasty....

OK, a 50% drop since 50% since September. Nothing to panic about, I'm sure you did the same as your peers and took advantage of when you share price was high to raise some cash.

oh, you didn't, oh dear

Well I hope those metallurgical results are good, but just a quickie - will you get them before the New Year (and I don't mean the Chinese one)?

Here is a funny chart - here are the PR headline grades from the Sandra PRs

They've become a bit average of late, can you drill some more good stuff, please?

XXXxxxXXXxxx 

TAG

Orex - Sandra Escobar - Metallurgical Testing

Orex have announced that they will be conducting some Metallurgical testing on the Sandra Escobar project.

Link to the PR here

Some points that I've noticed:
They still go on about it being a flat lying disseminated deposit. I disagree with this, as you have read in early posts, I feel that it is horizontal, low grade disseminated halo around vertical, high grade veins/stock work.


Here is a photo from Sandra Escobar the La Posta Stock work

Not many horizontal veins!

However, in the PR they give us 2 important pieces of information

1. The different metallurgical sample grades (50, 100, 150, 200, 250g/t Ag)
2. Different grind sizes (i.e. the sizes of the particles being tested - 75, 106 and 250 micron).

Sample grades

This is good, I explained before that a common trick is to just send high grade ore for testing, and this often skews the results as high grade ore is typically significantly different from low grade ore. Here are some photos from Sandra to demonstrate:

They look different, and they will have different metallurgical properties.

So reading between the lines:

• 50 g/t Ag - this will probably be the lower cut-off used in the upcoming resource calculations
• 250 g/t Ag - this material will probably be dominated by veining or disseminated mineralisation very close to the veining, so will have different metallurgical properties.

Orex are essentially testing all logical grades, but the critical results will be from the 50 g/t and 100 g/t samples as these areas will form the bulk (>50%) of the deposit. If they get crap recovery from the low grade zones, then there is no deposit here, time to move on.

Grind sizes.

General rule of thumb:

• coarse grind (e.g. 150 micron) - poor recovery due to poor liberation (i.e. unable to recover the very fine grains and encapsulated mineralisation).
• Fine grind - good recovery, but more expensive grinding costs, lower mill throughput

More simply:

From Runge et al (2013).

The finer the grind, the higher the cost

If you look at the sizes selected by Orex (150, 106 and 75 microns) that immediately tells us that the silver cannot be recovered by a heap leaching (particles sizes from 12-100mm), they need to crush and grind the ore to recover the silver.



My guess is:

• low recoveries (around 55%) from the 50 g/t zone
• good recoveries (around 75-80%) from the 200 and 250 g/t zones

The results from this study will make or break Sandra Escobar. Will we get some BS with only the most favourable results being released (along with the headline - 80% recovery from Sandra ore), and carefully relegating any poor results to the bottom of the PR?

Time will tell

Sandra - I sit and wonder why, oh?

Today there was another press release from Orex from Sandra Escobar. the results were disappointing, they clearly show that the silver mineralisation is NOT a disseminated blanket of silver but a disseminated halo around veins.
There is a silver lining, drill-hole 37 and 38 may have found a second, parallel zone.

For me, the results from the step out drilling was disappointing, with silver grades dropping the further we get from the core of the system.

Cross section (looking west) through the Main Zone

However, it isn't all bad news, Orex also released the assays from drill-hole 37 and 38. They were drilled 350m to the away from the main zone exploring an area where there appear to have been some historic exploration (google earth image shows some surface trenching and/or rock dumps.

Yellow dashed line = my guess extents of the Main Zone

  

 Both holes hit decent grades, but when we push through the promotion, we see exactly the same as when we have been seeing in the main zone. A narrow, high grade core with a moderately wide zone of lower grade mineralisation.

Again we can see that we have in both holes have a narrow (2-4m wide) zone of high silver grades that are surrounded by lower grade zone. We have seen this consistently in virtually every drill-hole on the property, but originally I had through that the silver zone would be intersected relatively deeply in these holes (around 70m depth), but they hit silver immediately. this is great news.

So how do holes 37 and 38 fit in to the big picture at Sandra? This is what I think is happening:

We are looking WNW here. Grey planes are proposed faults

I don’t think they have drilled the continuation of the main zone, but maybe they have discovered a second, parallel zone veining and silver mineralisation. If this zone is drilled to the SE, could it link up with the disseminated mineralisation with the main zone and form something bigger?

However, I would like to see a couple of things:

1. Additional drilling around holes 01 and 02 as the high grade mineralisation is relatively unconstrained
2. A few deeper drill-holes exploring the high grade mineralisation to depth. Drill-hole 18b hints that there could be some depth potential.

The market has responded to the new news, and it will be interesting to see what the upcoming resource statement says. I’m looking forward to it.

 

Again, updated leapfrog views can be found here (link)