The diamond formation, more commonly known as a diamond top, is a relatively rare chart formation used in technical analysis. When a diamond top forms, it forms at the conclusion of a long uptrend in price, and it indicates an imminent reversal of the trend. As such, the diamond top formation generates a very strong sell signal.
Traders and technical analysts recognize a diamond formation by first recognizing a head-and-shoulders formation (a peak and trough, followed by a higher peak and another trough, followed by a peak somewhere below the level of the previous peak: in other words, three peaks, the middle one being the tallest.) Four trendlines are drawn: one (ascending) from the first peak to the second peak, one (descending) from the second peak to the third peak, one (ascending) from the second trough to the low of the third peak, and one (descending) from the first trough to the second trough. The four lines altogether form a rough diamond shape, giving the chart its name.
The diamond top forms an overall descending trend channel, allowing traders to determine levels of support and resistance for the asset’s price as it enters a downtrend or a momentary reversal. However, if the lower support line of the channel is broken, traders consider it likely that asset prices will reverse and begin again to climb.