Dolomite-Ankerite

Carbonates: Dolomite-Ankerite

Composition: CaMg(CO₃)₂; iron substitutes extensively for magnesium; the name ankerite is used when Fe/(Fe + Mg) exceeds 20% (specialised characterisation is required to differentiate these minerals)

Crystal system: Trigonal; crystals commonly rhombohedral, also massive, granular and stalactitic forms

1.4.1
dolomite and sphalerite crystals
KS USA

Properties:

Vitreous lustre
Variable color; colorless, pale green or purple
White streak
Knife scratches easily (Mohs Hardness 3.5-4)
Average density
Three perfect cleavages not at 90^o to each other, often not apparent
Cleaves rather than fractures unless finegrained
Not ferromagnetic
Reacts very slowly with cold dilute hydrochloric acid (HCl) unless freshly powdered

Occurrence:

Dolomite occurs with calcite as extensive layers of dolomite rock interbedded with other sedimentary rocks. The metamorphism of dolomitic rocks produces marbles which contain various carbonates and silicates. Dolomite also occurs with quartz, other carbonates, oxides and sulfides in hydrothermal vein and replacement ore deposits.


1.4.2 pink crystalline dolomite KS district USA	1.4.3 pink crystalline dolomite KS district USA


1.4.4 pink crystalline dolomite KS district USA	1.4.5 white cleavable dolomite Thornwood NY USA

Dolomite is an important source of magnesium and calcium for agricultural and industrial applications.