Archie's Rule of Thumb for Mineral Deposit Economics

Archibald M. Bell (1906 - 1991) was a mining geologist and long time VP of Exploration for Noranda.  Later he was a successful consulting geologist.  Bell was an ore finder (Pamour, Timmins and Copper Mountain, Quebec).  He was inducted into the Canadian Mining Hall of Fame in 1995.  Bell is the source of Archie's Rule.

Source:  Canadian Mining Hall of Fame

Several years ago I came across a reference to "Archie's Rule" which is a rule of thumb method for evaluating the economic viability of a mineral deposit.

Simply and elegantly stated:  To be economic a deposit must have a recovered value of twice the all-in operating costs.  This allows for the covering of the capital costs.  The all-in costs includes mining, processing, refining, etc.  It assumes that the mine life will be long enough to extend over multiple metal price cycles.

Clearly not a  NI 43-101 level of evaluation, but a useful tool in evaluating mineral deposits.

The Pink and White Terraces of Lake Rotomahana, NZ

Greetings from Texas,

On April 26, 2016, Robin Wylie of the BBC posted an interesting story on the web about the rediscovery of the Pink and White Terraces on the north island of New Zealand. 
http://www.bbc.com/earth/story/20160427-a-natural-wonder-lost-to-a-volcano-has-been-rediscovered

Geologic map by Ferdinand von Hochstetter (1859) of the Rotamahana or Warm Lake (Left).  The sinter deposits are shown in yellow and are within a volcanic field.  Travel poster for the Pink and White Terraces (Upper right).  Bathers in the warm water of the hot springs (Lower right).

The Pink and White Terraces of Lake Rotomahana and the nearby volcano of Mount Tarawera are hot springs sinter deposits.  The sinter is composed of fine-grained quartz deposited by hydrothermal water of a geothermal field.  The Maori called the terraces taonga which means treasure.  They were also a popular tourist attraction for the well-to-travelers on the 19th century until 1886.  The terraces were "destroyed" by the eruption of Mount Tarawera on June 10, 1886.  The eruption was heard in Christchurch 400 miles away.  The locals, the native New Zealand Maoris, did not see the eruption from their villages.  However, 120 people, mostly Maoris were killed by the fallout of debris from the eruption.

Only one person saw the eruption.  Henry Burt was 7 miles east of the eruption and had a clear view of the volcanic eruption.  He told a journalist the lake looked like a "huge boiling cauldron bubbling in all directions."  After the eruption the terraces were no longed visible.  The New Zealanders had lost a valuable tourist attraction in the violent act of nature.

What we do have are beautiful watercolors of the area by Charles Blomfield, along with black and white photos by various individuals (some hand colored).  The watercolor is below.  The Pink Terraces are in the foreground and the White Terraces are in the distance.

Fortunately, recent scientific research has rediscovered the terraces below the waters and sediment of  Lake Rotomahana.  It is a fantastic story.  It is described in the research articles by C.E.J de Ronde, et.al. in the Journal of Volcanology and Geothermal Research:  Elsevier, volume 314, March 15, 2016.  One of the articles is titled:  The Pink and White Terraces of Lake Rotomahana:  what was their fate after the 1886 Tarawera Rift eruption?  (p.126-141).

 

 

 

Many thanks to Robin Wylie of the BBC for bringing this to the attention of the world and for the research by de Ronde and others for rediscovery the Pink and White Terraces of New Zealand.

 

It is worth your time to take a look at what else is available on the web on this story about the wonders of nature.

 

If you enjoyed this post, please comment.  dle