Gems from the Safe

This specimen of pyrosmalite (Mn) is regarded as the best of its type in the world due to the large size (up to 1 cm) of crystal clusters on calcite.

It was purchased in 1963 from Albert R. (Floss) Campbell who was a collector of fine minerals. It is the most valuable specimen (monetarily) in the Geoscience Australia National Mineral Collection.

Did you know that opals are Australia's national gemstone?

There are a number of opal shells in the collection that were found at Coober Pedy, South Australia. This world class opal region was once a marine environment during the Cretaceous (~146-65 million years ago) period when the shell was deposited and covered by sediment. During the Miocene (~23-5 million years ago) period, the original shell was replaced by opal.

This ruby (corundum) section in amphibolite was sent to Geoscience Australia in the 1960s by Hillside Properties for analysis work. In appreciation, the company donated a number of specimens to the collection.

Corundum is a crystalline aluminium oxide that comes in many varieties. For example, gem quality red corundum is referred to as ruby whilst blue varieties are sapphires.

Aspen in Colorado (USA) has produced large amounts of silver over the years including one of the worlds largest nuggets. This specimen from Aspen demonstrates the fineness and branch like structure that is typical for native silver.

The Roman's referred to silver as Argentum and hence its chemical element abbreviation is Ag.

Gem quality rhodonite is quite rare. Some of the finer specimens such as this have come from the famous Broken Hill lead-silver-zinc deposit which was one of the largest such deposits ever discovered. It produced over 300 minerals including the manganese-rich rhodonite. This is one of 6 pieces that have been faceted into fine jewels in the collection.

Dioptase is a popular mineral with collectors because of its rich green and blue colour. Named in 1797 by Hauy, dioptase means "through" and 'to see' in reference to the visibility of internal cleavage planes.

Stellerite is a type of zeolite. This zeolite is from cavities in volcanic rocks of the Warrumbungle mountain range, an area which contains some of the best zeolites in Australia. Some of the cavities discovered at the site were tens of metres in length.

Anglesite is a secondary lead sulphate mineral ranging in colours, in this case the very rare green crystalline mineral. Named after the type locality, Parys Mine on the island of Anglesey in Wales, U.K.

Watermelon tourmaline is so named for the striking balance of green on the outer rims of the mineral with a white inner layer followed by variations of orange-red or pink.

Amazonite is more typically coloured green than the blue variety here. It is thought that the colour is derived from an elevated lead content. Named after the Amazon River in Brazil, amazonite is a microline feldspar.

Calcite is a common mineral but what makes this specimen valuable is its large size, shape and colour.

Rhodochrosite is a manganese mineral which when transparent, raspberry coloured and in crystal form is rare and commands high prices by collectors. It is the national gemstone of Argentina.

A true gemstone, this golden yellow variety of beryl is referred to as heliodor. Note: emeralds are the green variety of beryl and aquamarine is a blue-green variety of beryl when gem quality.

Known from only a handful of localities, such as the Black Pine mine, Montana, USA, the copper-zinc mineral veszelyite is an extremely rare gem with crystal sizes usually less than 10 mm.

Brazilianite is typically found in granite pegmatites and is named by Frederick Harvey Pough and Edward Porter Henderson in 1945 for the type locality country, Brazil, where it was first found.

Some of the finest specimens of stolzite come from the Broken Hill lode in Australia. A lead tungstate with the formula Pb(WO4), it is a rare secondary mineral in the oxidized zones of hydrothermal deposits.

Pyromorphite comes in a variety of colours, yellow, green, brown, grey, and colourless. It is a secondary lead mineral with barrel-shaped hexagonal prisms, in clusters often lining cavities.