16g Feldspar Pseudomorph after Scapolite Specimen B

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These very interesting and rare specimens are Pseudomorphs of Feldspar after Scapolite from the Mary Kathleen Mine, Rosebud Station, Cloncurry Shire, Queensland, Australia. As far as I can tell the only other place worldwide that this particular pseudomorph has occurred is the Griffith township, Ontario, Canada.

This piece weighs 16g and measures 4cm x 2cm x 2cm.

The Mary Kathleen Mine was an open pit Uranium mine located east of Mt Isa that has been closed since about 1984. Mining was carried out from 1956 to 1963 and 1975 to 1982, and originally contained about 10,0000t of U2O3 and 200,000t of rare earth oxides (Scott & Scott, 1985).

The mine produced almost 9,000 tonnes of 'yellowcake' (uranium oxide), it was approximately 250 meters deep, 4 kilometres wide at the top and 100 meters wide at the bottom. One of Australia’s oldest Uranium mines, it was initially developed to supply the United Kingdom Atomic Energy Authority, and it later supplied uranium to Japan, Germany, and the United States.

In the 1980s, unions and environmental groups actively campaigned against Uranium exports, particularly from the Mary Kathleen mine. Issues were the possible dangers of leaked radioactive material, how the Australian Uranium might be used, and the government financial support needed to keep the mine open. Concern over security was also expressed, after 2 tonnes of 'yellowcake' from the mine were found in Sydney.

When production ceased in 1984 at the mine, the mine and town were dismantled and sold in what is said to have been Australia’s largest auction. Now a ghost town, part of the road systems, parks, and concrete slabs of the once existing buildings are all that remain of a flourishing community of 1,000 people. Four wheel drive is needed to access areas of the mine.

Scapolite:-

Named in 1800 by José Bonifácio de Andrada e Silva from the Greek skapos meaning (a shaft, rod) in allusion to the long prismatic habit of the crystals. Scapolite is a name used for a group of aluminosilicate minerals that includes Meionite, Marialite and Silvialite.

A pseudomorph is a mineral that takes on the outward form or shape of another mineral due to a process of replacement or alteration, even though its internal chemical composition and structure are different. Essentially, it's a mineral that "impersonates" another.

Feldspar:-

Very briefly, the term Feldspar is used to identify a very large group of minerals. In fact, it is used to describe any mineral which consists of framework Aluminium , Oxygen and Silicon atoms plus an additive. All minerals in this grouping have the same crystalline structure. The Feldspar group has nearly 20 recognized members, but only nine of those are common.  These may be divided into two types of Feldspar: Plagioclase and Alkali. Many people would be familiar with more common names of some types of Feldspar. For example Amazonite, Albite and Labradorite are all types of Feldspar.