Ðèñ. 3. Ñëåâà — ïîëèñèíòåòè÷åñêèé äâîéíèê ñåãíåòîâîé ñîëè; ñïðàâà — ïîëèñèíòåòè÷åñêèé äâîéíèê òðèãëèöèíñóëüôàòà, âûÿâëåííûé òðàâëåíèåì (ôîòîãðàôèÿ â îòðàæ¸ííîì ñâåòå).