A small town located West of Gunnedah and East of Coonabarrabran, geologically notable for its volcanic rocks, mostly in the Garrawilla volcanics and Bulga complex (Bean, 1974).

The Garrawilla volcanics, extensive Triassic-Jurassic olivine basalt flows, commonly contain some important deposits of zeolites and other minerals, and at least 90 occurrences are known (England, 1989). Most of the best specimens have probably come from the Garrawilla and Mitchell creeks, on the Garrawilla, Glendowda and Mt Mitchell Stations, though there are many similar zeolite locations in the area so it’s hard to be sure about individual specimens. Specimens have also been variously labelled as Tambar Springs (some 25 km away from Garrawilla), Mullaley (35 km), Coonabarabran (45 km) and Gunnedah (60 km).

It is considered that the basalt-hosted deposit at Mullaley is the only significant source of prehnite in the district and that any prehnite specimens labelled as being from Gunnedah, Garrawilla, Tambar Springs or Coonabarabran are all from Mullaley (see Kennon & Carr, 2009).

The prehnite deposit is located on a sheep station called "Careona" (1999).

Geochronology

Mineralization age: Mesozoic : 201.5 Ma to 171.5 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Phanerozoic
	Mesozoic
		Jurassic
			Middle Jurassic	ⓘ Basalt (youngest age) 171.5 Ma
		Triassic
			Late/Upper Triassic	ⓘ Basalt (oldest age) 201.5 Ma

Other Regions, Features and Areas containing this locality

References