dolomite after calcite (?)

TSNB444
Specimen
Feinglos, M.N.New, D.
Exhibit 1. Dolomite after calcite (?); 95 mm.
Exhibit 1. Dolomite after calcite (?); 95 mm.
Image Credit: Malcolm Southwood
Exhibit 2. Dolomite after calcite (?); 95 mm.
Exhibit 2. Dolomite after calcite (?); 95 mm.
Image Credit: Malcolm Southwood
Exhibit 3. Dolomite after calcite (?); 95 mm.
Exhibit 3. Dolomite after calcite (?); 95 mm.
Image Credit: Malcolm Southwood
Thumbnail by 1Thumbnail by 2Thumbnail by 3

Specimen Title

dolomite after calcite (?)

Associated Minerals

(not assigned)

Principal Mineral

Dolomite

Precursor Mineral (Uncertain)

Calcite

Size

Cabinet; 95mm

Provenance

Smith, A.G.

Collection

Geoscience Australia; R38858

Entry Number

Specimen; TSNB444

Description

An epimorphous "shell" of peach-coloured dolomite after calcite (?). The precursor mineral (probably calcite) has been completely disolved away leaving a ropey texture on the convex surface of the dolomite (Exhibit 1) and a pattern of angular molds on the concave surface (Exhibit 2). A side-by-side comparison of the two surfaces is presented in Exhibit 3. While not reliably diagnostic, these patterns are consistent with a trigonal carbonate, probably calcite, as the precursor mineral. The colour of the dolomite surfaces is likely due to the partial oxidation of iron in the dolomite lattice. There are no other minerals associated with the dolomite.

The specimen was formerly in the A. Glen Smith Collection which was donated to the Australian National Museum in the mid-1970s and is now housed at Geoscience Australia.