Mineral Outcrop Observations

Like in outcrops, the data that ditches can give is in reference to minerals and attle to box rocks and the relation between different elements.

D) Sampling

If the ditch cuts through mineralized rocks or mineral evidence (iron peaks, hydrothermal alterations, disseminated sulfurs, etc.) the sample will be taken making an incision using a hammer and chisel: with a vertical furrow if the mineralization is joined to a strategic horizon or a horizontal veinlets-stratum; horizontal furrow, in a layers context or vertical veinlets or in disseminated form.  

Each sample with the object of quantity determination must be done utmost carefully.

Case of a sub-vertical veinlets (with >0.40cm)

The veinlet is freed at about 50cm of height and the upper altered & fractured part is eliminated.

Once that is done, sampling operations begin (see fig. 6). The surface that will be sampled when possible - be it flat or perpendicular to the walls of the veinlets – will be washed very carefully with water and a brush. Two parallel lines will be marked 15cm apart and aligned with the walls of the veinlet, with a calk or paint. Within these lines a 5cm furrow will be made. It’s important not to deepen the smooth or hard parts too much, since the difference of hardness correspond to different mineralizations. Irregularities can give an erroneous idea of pitch.

To verify the regularity of a furrow, a wood model can be made like in fig. 7.

The parts of the veinlet that fall will be carefully picked up with a board or sash placed on the floor, that will later be cleaned up and all the material will be placed in a container. In a second task the volume of material will be reduced depending on the task demand.  

The distance from furrow to another can vary depending on the case from 1-5mt.

Case of a more or less flat outcrop
The technique used doesn’t differ from that used for veinlets: the furrows are made perpendicularly to the alignment of the mineralization and each sample will represent the length of a variable furrow from 1 to 5cm.

Sampling through “cuttings” of the perforation holes

This method is only applicable when the location of the outcrop is accessible by transport that can carry a compressor.

Perpendicular to the outcrop parallel profiles are traced with a distance of 10-20cm between them & throughout the length of each one with a pneumatic hammer small holes will be made every 1 or 1.5cm, with 45 degrees of horizontal inclination.

At the opening of each hole place a sucker or recuperator, that will pick up the fragments in a sack placed at he base. All the fragments with the same profile will makeup a sample and will be sent to the laboratory for analysis.

Case of a vertical wall

In the case with a wall with mineralized horizontal or slightly inclined layers, sampling will be done by vertical furrows with an interval that can vary from 1 to 5mt. 

The dimensions of the furrow will always be 15 x 5cm of depth.

E) Sample preparation:  Grinding

Samples take during the hammer prospecting phase normally have a volume that doesn’t go over 20 l.

So it is enough breaking in a mortar, once the larger pieces have been broken with a hammer or sledgehammer.

This grinding should take the sample down lower than 1mm.