Northern Queensland fossicking

Gem-quality feldspar can be found on Moonstone Hill between Hughenden and The Lynd. The material is suitable for cutting as faceted gems or cabochons and some rarer material may exhibit the bluish adularescence of moonstone. Attractive specimens in matrix are also found. The locality is surrounded by Blackbraes National Park.

Moonstone Hill is a general permission fossicking area and fossickers must comply with the special conditions of access (see below).

Access

Moonstone Hill is a low isolated hill on the east side of the Kennedy Developmental Road (unsealed) about 90km south of The Lynd. The Reserve is 5km north of the Blackbraes turn-off, or about 16km north of the Chudleigh Park turn-off.

Look for a simple wire gate in the fence and a track leading to the hill. A sign showing the conditions that apply is erected on the reserve and boundary markers have been surveyed in.

Facilities

Camping is available at Blackbraes National Park. Camping permits are required, and fees apply.

Map

• Moonstone Hill feldspar locality map (PDF, 303.3 KB)

Fossicking notes

Late Cenozoic basaltic volcanism is well developed in northern Queensland in 12 separate provinces. Moonstone Hill is within the Chudleigh Province, which is characterised by broad, partly dissected lava plains between numerous pyroclastic cones, some composite cones and several lava shield volcanoes. Moonstone Hill is one of several scoria vents that are surrounded by flat-lying basalt lavas, some of which were erupted from the vents. Scoria (lava with a high proportion of gas bubbles) is exposed on top of the hill and is typically reddish-brown in colour, and characterised by its vesicular texture. The feldspar occurs as megacrysts filling some gas cavities in the lava. The lava plains overlie older metamorphic rocks of Precambrian age, Palaeozoic sediments and granitoids, and Cretaceous sediments.

The feldspar from this locality has been identified as anorthoclase, an alkali feldspar in which sodium is in excess of potassium, which is unusual as anorthoclase-moonstones are uncommon and somewhat of a rarity for collectors.

Generally the material is colourless and transparent, but some is milky white to yellowish and translucent to opaque. Some specimens show a silvery-white to bluish adularescence (presumably because of separation into albite and othoclase crypto-perthitic layers) and hence can be classed as moonstone.

Gem-quality material commonly occurs as blocky cleavage fragments of 10–30 carats and rare specimens 5–6cm in length. A lot of material is unusable for cutting due to incipient cleavages, or fractures and other inclusions, but clean sizeable material is common. The material has weathered out of the host rock and can be found on the ground surface or in the soil around the lower flanks of the vent.

Specking the ground surface and simple shallow excavation and dry sieving are the best methods to use.

Special conditions

• Do not light any fires.
• Leave fences and gates as found.
• Bring in your own portable drinking water.
• Do not enter the adjacent national park for fossicking.
• Remove all rubbish.