Non-Chemical Microscope mineralogy (Help)

[goldshark]

The CC ores are very amendable to cyanide heap leaching. It is a hard permit to get, I always wondered how they (Ashanti), at the time, were able to procure a permit in a state that has outlawed the use . I guess money does talk. I believe the new pit, with the higher grades, have built a floatation mill. Imitation is the sincerest form of flattery. Best to get some float cells, if you and the amigos are going to give it a real go. 135 ppm is around 4.5 Troy per tonne. Good enough to invest in, if you have a few million sitting around, and more of this material.

 

[Southfork]

For a few thousand dollars you could be crushing / milling ore and recovering gold. One good rock and it pays for itself some days we make money.

 

[auheyyou]

There are two types of microscope used by geologists for the identification of minerals and rocks. The mineralogical microscope which is used to analyze rock samples that have been made into thin sections (about 35 microns thick). Polarized light from below passes through the thin section and then through another polarizing filter above the slide. The individual rock forming minerals can be identified due to their particular birefringence and other characteristics. The other type of microscope is the metallographic microscope which is used to examine an ore (or an alloy) sample which has been cut flat with a diamond saw then polished to a very fine surface. The sample in the microscope stage is illuminated from above at a 45 degree angle (as light will not pass through most native metals and ore minerals). The various minerals can be identified by their visual characteristics and the associations of the minerals in the rock can yield information about the processes of mineralization that occurred in the rock.

 

[goldshark]

There are two types of microscope used by geologists for the identification of minerals and rocks. The mineralogical microscope which is used to analyze rock samples that have been made into thin sections (about 35 microns thick). Polarized light from below passes through the thin section and then through another polarizing filter above the slide. The individual rock forming minerals can be identified due to their particular birefringence and other characteristics. The other type of microscope is the metallographic microscope which is used to examine an ore (or an alloy) sample which has been cut flat with a diamond saw then polished to a very fine surface. The sample in the microscope stage is illuminated from above at a 45 degree angle (as light will not pass through most native metals and ore minerals). The various minerals can be identified by their visual characteristics and the associations of the minerals in the rock can yield information about the processes of mineralization that occurred in the rock.

What does " crossed Nichols " mean?

 

[user 69385]

What does " crossed Nichols " mean?

Nicol lens or polarizers are made of two calcite prisms glued together. They are used to analyze plane polarized light.
It is actually more involved than this and there is a whole course on optical mineralogy that covers it properly.

 

[auheyyou]

The path of light in the microscope comes from a lamp at the base. That light passes through infrared (and maybe ultraviolet) filters to protect your eyesight. The light beam passes through the lower Nicol polarizer and then up to the microscope stage and through the thin section microscope slide then up the barrel of the microscope, through the objective lens and into your eye. The minerals are mostly clear and some are colored. The observer can determine some of the characteristics of the minerals such as texture and color. The barrel of the mineralogical microscope also contains a quarter-wave plate and an upper Nicol that can be slid into position to interact with the light path. If there was no slide on the stage and the Nicols were crossed the observerer would see an almost dark field of view. When a slide is in place and the Nicols are crossed the different minerals in the rock sample show amazing birefringence colours. As the stage is rotated those colors change and the different minerals in the rock sample can be identified and the mineral boundaries can be clearly seen. Opaque minerals and native metals must be viewed with the special metallographic microscope.