Page 11 - js expolaratıon

Each sample bag is labelled with a unique identification number from a ticket book and the duplicate
ticket is torn out of the book and placed in the bag with the sample. When the core has been cut it is
submitted to the laboratory for assay along with the required number of blanks, standards and
duplicates for proper quality control purposes.

Interpretation
When the results of the assays become available, they are plotted along with observations from the
logging onto cross-sections. This enables the results to be easily visualised and interpreted by the
geologist.
Intervals of significant mineralisation are identified and reported as the average grade over an interval
of drill-core with corrections applied to account for the angle of the hole. This is how the true thickness
of mineralisation is obtained.
Investors should always be on the lookout for drill hole data that has been reported without corrections.
Some companies have reported results of drilling that are at an oblique angle to the mineralisation
without any corrections, giving apparently very wide zones of mineralisation. In extreme cases some
companies may even drill parallel to the mineralisation with seemingly hundreds of metres of
mineralisation. Therefore, company exploration reports should always be read with care to avoid any
misinterpretation of the data.

What the –IC? An Introduction to Alteration

Overview
Alteration is a term that appears in almost every junior mining company press release or project
description, often repeated many times in a single paragraph. It is usually prefaced by a strange
assortment of words ending in –ic, like potassic, advanced argillic or hematinic.
Entire journals, textbooks and theses explore in detail the formation of alteration minerals and the
patterns they form around the world’s most important ore deposits. Understanding alteration is
essential to understanding where the next big discovery will be found.

What is alteration?
Ore deposits form in many different ways and valuable minerals accumulate in igneous, metamorphic
and sedimentary settings.
The most common ore forming processes involve the relocation and concentration of metals by fluids.
Some fluids are released by a magma, others are hot, aqueous fluids circulating deep within the crust
or cooler groundwater’s percolating down from the surface. Many are a complex combination of these.
In most cases alteration is caused by these fluids moving
through the tiny spaces between the minerals in a rock and
along structures like faults.

Alteration involves the modification and replacement of the
original minerals in a rock with a new suite of minerals with
different chemistry.
Minerals can be altered by sudden changes in temperature
and pressure too.

New alteration minerals are deposited in cavities or
fractures, change the chemistry of existing minerals or
replace them with new minerals entirely. Replacement of
one ore mineral by another, or by a mineral formed during weathering is common in many ore systems.
Sodium- and calcium-altered porphyritic granite from Yerington, Nevada, USA (jsjgeology/flickr)

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