Daily Journal

Day 15 | August 1, 2005

Here are the olivines!

Throughout the expedition we have been stressing the need to collect good olivine samples. They contain the volatiles we are interested in measuring. In effect, the olivines act to trap the volatiles - sometimes in melt inclusions (samples of the magma) and sometimes within the matrix of the mineral itself - and to transport them to the surface. Today, on Hachijojima, we were rewarded for our efforts traveling around the Izu Islands by finding olivines in abundance!

The first stage in our daily routine is to look closely at the rocks, preferably with the aid of a hand-lens. Our team member, Masaki Takahashi from the Geological Survey of Japan, is shown getting up close to some lavas. Eureka! This particularly sample contains many of the precious olivines. The crystals are a deep green color and quite large (1-2 mm in diameter). Usually, we would collect about 2-3 kg of this type of rock depending upon the olivine abundance. Then, we would transfer the samples back to the hotel for shipment back to the lab for preparation and analysis. This locality is so good, however, that we could collect pure olivine crystals straight out of the rocks. If only they were all this easy!