For Understanding twinning law
身近な材料で双晶の形式を理解する
応用例：偏光顕微鏡観察で斜長石の双晶を観察後に結晶相互の関係を知る。
準備：マッチ箱の各面が特定できるよう塗色する
Prepare some matchboxes marked or painted to
distinguish each face
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垂直双晶 Normal twin
双晶前 Before twinning
接合面に垂直な軸のまわりで回転
Rotating around the twin axis normal to the
composition plane.
↓
垂直双晶 Normal twin
垂直双晶の例：アルバイト双晶，接合面は(010)
Example of normal twin: Albite twin, with the
composition plane (010)
Width of photo is about 2mm.
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平行双晶 Parallel twin
双晶前 Before twinning
接合面に平行な軸のまわりで回転
Rotating around the twin axis parallel to the
composition plane
↓
平行双晶 Parallel twin
平行双晶の例：カールスバド双晶，接合面は(010)
Example of parallel twin: Carlsbad twin, with
the composition plane (010)
Width of photo is about 2mm.
---------------------------------------------------------
複合双晶 Composite twin
双晶前 Before twinning
垂直双晶 Normal twin
垂直双晶に平行双晶を加える（複合双晶）
Parallel twinning is added to Normal twin.
↓
複合双晶 Composite twin
複合双晶の例：アルバイト-カールスバド双晶，接合面は(010)，双晶軸が(010)面上でc軸に垂直な軸
Example of composite twin: Albite-Carlsbad
twin, with the composition plane (010) and the twin axis normal to c-axis on
(010)
Width of photo is about 2mm.
=============================
そのほかの双晶例 The other twins
バベノ双晶 Baveno twin
(021)を接合面とする垂直双晶 Normal twin around the composition plane
(021)
(010)と(001)のへき開面(線)に斜交 Oblique against cleavage (010) and (001)
Width
of photo is about 1mm
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ペリクリン双晶 Pericline twin
菱形断面を接合面とする平行双晶 Parallel twin, with the composition plane of the rhombic section
Width
of photo is about 1mm
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アルバイト双晶とペリクリン双晶 Albite twin and pericline twin
Width
of photo is about 1mm
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