Page "Crystal twinning" Paragraph 6

If several twin crystal parts are aligned by the same twin law they are referred to as multiple or repeated twins.

If these multiple twins are aligned in parallel they are called polysynthetic twins.

When the multiple twins are not parallel they are cyclic twins.

Albite, calcite, and pyrite often show polysynthetic twinning.

Closely spaced polysynthetic twinning is often observed as striations or fine parallel lines on the crystal face.

Rutile, aragonite, cerussite, and chrysoberyl often exhibit cyclic twinning, typically in a radiating pattern.