The Tor Limestone was named at Tor Point, a high ridge north of June Canyon below and northeast of Masket Peak, in the northern Toquima Range (Kay, 1960).

The Tor Limestone is in thrust contact with underlying units (Ordovician Antelope Valley Limestone) except on the north side of Ikes Canyon where it overlies the Masket Shale (Roberts Mountains Formation) along a sedimentary contact (McKee and others, 1972). Corals suggest a Late Silurian age, while conodonts and graptolites from the same and higher strata suggest an Early Devonian age (McKee, 1976). The Tor correlates with the lower portion of the McMonnigal Limestone and is a time-equivalent of the upper portion of the Roberts Mountains Formation.

The Tor Limestone is a massive to structureless, white to light-gray, coarse-grained, bioclastic limestone which retains much of its original texture. These thick-bedded limestones form prominent cliffs and peaks in the northern Toquima Range. Kay and Crawford (1964) describe the basal 30 feet of the formation at Ikes Canyon in the Toquima Range as dark, poorly to evenly bedded, sandy to silty, crinoidal limestone with thin shale partings. The overlying limestones are massive and silty and contain abundant echinoderm, coral and stromatoporoid debris, thin brachiopod coquina beds, and algal structures.

Sections of the Tor limestone are structurally complicated, with the upper contact of the Tor being a thrust. Kay and Crawford (1964) estimated a thickness of 500 feet on the north side of Ikes Canyon, and about 200 feet of the Tor Limestone is present at the type section in the Toquima Range.

The Tor Limestone is only recognized in a small area within the northern Toquima Range.

The Tor Limestone was considered a biostromal or reef facies of the McMonnigal Limestone by Kay and Crawford (1964). Matti and McKee (1977) felt that the Tor Limestone represented shoal water carbonate buildup along a linear north-south-trending ridge which they called the Toiyabe Ridge. Turbidite sheets were shed radially from the Tor Limestone, and were deposited within the McMonnigal Limestone and the lower portion of the Masket Shale (Matti and McKee, 1977).