English: Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light.

The thin section is only slightly oriented and shearing has barely effected to the rock. The grain size is quite large and carbonate content is high.

Tetraferriphlogopite is the main mineral of the thin section and it forms 50 % of the area. Grains are usually 1-3 mm in diameter and oval in shape. Smaller elongated chips are common between the grains.

Carbonates form one third of the thin section area. Calcite is the dominating carbonate mineral. Carbonates look unaltered in the thin section and they are grown into large mineral aggregates. Dolomite grains are commonly smaller than the calcite grains. The diameter of the grains is 0.2-2 mm.

Apatite is widespread mineral in the thin section, and usually found as big rounded grains. The grains are 0.5-2.5 mm in diameter and form 10 area-% of the thin section.

Amphiboles are found as variable sized sub- to euhedral grains. Biggest crystals are > 3 mm in diameter, and usually they are > 0.5 mm in diameter. However, even tiny crystals are found. Amphiboles form 7 area-% of the thin section.