Sparry Calcite

Many limestones contain large crystals of calcite, commonly on the order of 0.02-0.1 mm, that appear clear or white when viewed with a hand lens or in plain light under a polarizing microscope. ^[1] Such crystals are called sparry calcite. ^[1]

Distinguishing Features

Sparry calcite crystals are distinguished from micrite by their larger size and clarity and from carbonate grains by their crystal shapes and lack of internal texture. ^[1]

Occurrence as Cement

Some sparry calcite can be seen under the microscope to fill interstitial pore spaces among grains or to fill solution cavities as a cement. ^[1] The presence of sparry calcite cement in intergranular pore spaces indicates that grain framework voids were empty of lime mud at the time of deposition, suggesting deposition under agitated-water conditions that removed fine mud. ^[1]

Origin by Recrystallization

Sparry calcite can also form in ancient limestones by recrystallization of primary depositional grains and micrite during diagenesis. ^[1] Sparry calcite formed by recrystallization may be very difficult in some cases to differentiate from sparry calcite cement. ^[1]

Interpretive Significance

It is important to distinguish between the two types of sparry calcite because incorrectly identifying recrystallized spar as sparry calcite cement can cause errors in both environmental interpretation and limestone classification. ^[1]

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