On Santorini island there are a few opportunities to discover minerals. In any case one has to hike and to be patient to find nice collectable minerals. Nice samples are something very rare and precious to find on this volcanic island. The volcanic rocks on Nea Kameni and Palea Kameni islands itself contain only a few nice samples. The most dacites are very poor in nice samples. Sometimes there are bubbles containing zeolithe crystals. You may find such samples on big boulders, but it is nearly impossible to cut samples with an geological hammer of 1-2 kg.
Sometimes there are rhyolithic rocks like the pillow lavas at Acrotiri which contain hydrothermal minerals like quartz, opal and even chalcedony or zeolithe.
Sometimes there were more rare rocks thrown out by phreatic eruptions. Their origin may me in deeper layers of the earth. The most interesting rocks for mineral collectors are the so called "skarn". These rocks were created, when limestone or marble was falling into an active magma chamber. They have changed their chemistry and they contain rare minerals. Sometimes you may find them on Palea Kameni island, close to the eruption crater (lake) of 1700 A.D. and they may contain green or brown garnet crystals. In the area of Ia I discovered a skarn rock of 30 cm with the biggest pyroxene crystal I ever found.
Another type of geological conditions to offer minerals, are the metamorphic, non-volcanic rocks of Athinios port which are shists and marbles. There are many tectonic faults that have been covered with ores by hydrothermal solutions. There you may discovery galena and copper minerals. They can be discovered by their rusty colours and they are close to the road towards the harbour.