The Martha deposit is an economic giant epithermal gold
deposit, with mined and unmined resources of more than 218 000 kg (7 Moz) Au.
The Au-Ag, base metal sulphide-bearing quartz lodes in the Martha deposit form
an extensive braided pattern within hydrothermally altered andesite wall rock.
There are five main quartz lodes:
1.
Martha,
2.
Welcome,
3.
Edward,
4.
Empire, and
5.
Royal.

Information from historic mine plans and reports has been
used to determine the depth distribution of economic ore within the Martha
deposit. Economic ore (average of 10 g/t Au) in the Martha underground mine was
at a maximum width and strike length between a vertical depth of 160 and 350 m.
Below this depth the quartz-sulphide lodes continue, but the grade declined to
sub-economic grades (< 4g/t Au) at about 575 m depth and economic ore shoots
were localised, mainly on the hangingwall side of the lodes. Samples from
exploration drill holes indicate that this decrease is associated with a depth
zonation from electrum-bearing Zn-Pb-Cu-Ag sulphide ore (average 10 g/t Au) to
sub-economic (< 2 g/t Au) electrum-poor Zn-Pb sulphide
mineralisation.