Tintenbar NSW

 

Tintenbar is the geographical name given to an area in north eastern NSW that encompasses a number of opal discoveries and opal fields within the surrounding areas. Tintenbar is essentially the only area that has produced commercial quantities of precious opal from a so called “volcanic geological environment”, in NSW. Other small occurrences of precious opal that will be described later are an occurrence near Bathurst in NSW known as “Rocky Bridge Creek” and a small occurrence near the Warrumbungle mountains, Coonabarabran and known by the name of the small locality of Tooraweenah.

Opal from Tintenbar has its own set of gemmological attributes that separate it from the more prolific precious opal producing areas within the Great artesian (Australian) basin which are considered to be from a “sedimentary geological environment”.

So let's start with a little geography and geology. The Tintenbar region is in the far north east of NSW just below the border between NSW and Queensland. The region is much more famous for growing agricultural products such as sugarcane, and is general one of the most productive farming districts in NSW. Perhaps it goes without saying that part of the reason for the success of agriculture is the the fertile soils provided by the volcanic nature of the soil in the area.

The predominant feature that is observable in this area is the Mount Warning volcano. The remnant core of the volcano is the remnant of the much larger Tweed volcanic province. The mountain was so named during the voyage of Captain James Cook which transversed the east coast of Australia in 1770. The name is issued as a part of the warning for the beginning of the most southern area of the Great Barrier Reef.

From a geological point of view, the opal occurrences are associated with the weathered basalts and volcanic-clastics or tuffs erupted by the volcano. 

The opal is found in the weathered parts of the Lismore basalt. The Lismore basalt is made up of three lava flows in the area and are described as the basal unit of the Lamington volcanics of early Miocene age (5.3 - 23.7ma). The precious opal occurs mostly between the the junction of the first and second lava flows as loose nodules in the soil  and as amygdale (cavities) in the decomposed and weather vesicular basalt.

Historical information says that the deposit was discovered in 1901 by a Mr D Munro but not exploited by Mr JH Morris who commenced mining in 1919 the report by MacNevin and Holmes (GS1979-268) states that $7,600 worth of precious opal was recovered between 1919 and 1922.

Tony Smallwood and Isaac, displaying his collection of Tintenbar Opals.