Mount Gibson, Tablelands Region, Queensland, Australia
|Latitude & Longitude (WGS84):||17° 38' 9'' South , 145° 12' 26'' East|
|Latitude & Longitude (decimal):||-17.63611,145.20750|
|Other/historical region names associated with this locality:||Innot Hot Springs|
Mount Gibson near Innot Hot Springs in north Queensland is well known by fossickers as a collecting locality for gem topaz. Innot Hot Springs is on the Kennedy Highway between the small townships of Mount Garnet and Ravenshoe. Mount Gibson is about 5km north-west of Innot Hot Springs. From the highway take the Broken Gully Road and travel 1.7km to a grid/steel gate (please close gate upon entering) and continue to the main entrance sign at Condon Gully. Conventional vehicles should only go as far as Gibson Gully. Access by foot or 4WD vehicle is recommended beyond this point as tracks to the main diggings are steep and gully crossings are very rough, with many washouts occurring after rain.
Mount Gibson consists mainly of hornfels resulting from thermal metamorphism of sedimentary rocks of the Silurian to Devonian Hodgkinson Formation by a composite granite batholith of Permo-Carboniferous age. The hornfels occurs as a pendant within the roof zone of the batholith that, in this area, comprises a medium-grained alkali feldspar granite (Pinnacles Granite) and smaller bodies of microgranite, pegmatite and aplite. Late stage topaz-bearing intrusions related to that appear to be the source of the gem topaz and associated cassiterite. Much of the area is strongly mineralised and many of the creeks and gullies in the vicinity have been worked for alluvial tin (cassiterite). Topaz, quartz and cassiterite are the main minerals found. Crystals showing good forms and clarity are common. Topaz is usually colourless but rare golden and blue colours have also been found.Diggings are located on the lower slopes of Mount Gibson to the south-east of the trig station. This area is known as Glittering Star and contains numerous shallow pits, trenches and shafts.
Other diggings known as Patricia (The Crystal and Pattersons) are located less than 1km to the west. Shallow pits and trenches have been worked in 2 adjacent areas on the northern side of a small north-westerly trending ridge. At the north-western end (The Crystal), massive white quartz crops out prominently. Several shallow pits have been dug in search of vughs in the quartz outcrop but most of the pits are located in the scree slope below. Further to the southeast (Pattersons) shallow pits have been dug in scree material and quartz-greisen rock, which contains many vughs and possibly crystals.
Simple dry sieving methods are used to search for gems, as water is generally scarce.
Alluvial tin mining.
Much Topaz has been found in this region, particularly north of Innot Springs near Mount Gibson.
Mount Garnet is another town further west of Innot Hot Springs.
Mineral ListMineral list contains entries from the region specified including sub-localities
5 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
358.9 - 419.2 Ma
Age: Devonian (358.9 - 419.2 Ma)
Stratigraphic Name: Hodgkinson Formation
Description: Mainly pale to dark or greenish grey, fine to medium-grained, medium to thick-bedded, quartz-intermediate greywacke, rhythmically interbedded with siltstone and mudstone; minor conglomerate, conglomeratic greywacke. Sparsely fossiliferous.
Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia). 
Localities in this Region
- Tablelands Region
Johnston, C., Chappell, B.W. (1992) Topaz bearing rocks from Mount Gibson, North Queensland, Australia, American Mineralogist Vol 77, pp303-313.