Sunday, January 5, 2020

Aloha! Hawaiian Treats!

I just got back from spending Christmas week in Hawaii and was once again amazed by the rock formations and lush landscaping I saw there!

This is me six years ago holding up the side of a lava tube at the Thurston Lava Tube also called the Nahuku in Volcanoes National Park on the Big Island.  I'd been hoping to do it again, but I was told that you can't do that lava tube anymore, it's under the recent lava flows. It is a reminder to all of us not to wait to get out and see the natural wonders of our planet. They may seem like they'll be there forever, but changes are always happening--and we never know where or when.

When I was in Hilo, I visited the Lyman Museum (look for a review of it in an upcoming Rock & Gem). Not surprisingly, it features some volcanic materials.

The museum displayed “volcanic bombs” from eruptions. These are composed of basalt. When the liquid is shot into the air, it comes together, twists around, and falls to earth. The shape tends to be oval, like a football. The bomb may be solid or hollow and they are collected as oddities for their shapes and textures.

Volcanic Bomb at Lyman Museum
Pele's Hair from Lyman Museum
Volcanic bombs and small sharp black splinters are not the only interesting form that falls from the eruptions. There is also Pele’s Hair, Pele’s tears, and spatter. The hair is formed when lava is flying through the air and it stretches because it’s still molten. The resulting thin strands are glass and they sometimes have a droplet at the end. Some call those droplets Pele’s Tears. Frankly, Pele's Hair looks a bit like the hair I take out of my hairbrush; silvery gray with a touch of brown.

Another formation that is called Pele’s Tears is the peridot crystals that can form in olivine. The spatter is exactly what it sounds like, bits of lava that fall to the ground.

Olivine with a few Peridot crystals
The Hawaiian Islands are fascinating for many reasons, especially the chance to see geology in action! It does have some minerals that lapidary artists and mineral collectors look for, but they are largely in microscopic amounts of labradorite, feldspar and plagioclase. The one you’re most likely to find is olivine. Olivine is a green mineral that has very little silica and a lot of magnesium and iron. It is the least stable mineral on the earth’s surface; when olivine gets weathered, it pseudomorphs into iddingsite.  While olivine is a mineral because it has an identifiable crystalline structure, iddingsite passes through many phases of change and so it is referred to as a rock, not a mineral. When the olivine is mixed with pyroxene, it becomes peridot.

Lapidaries have been known to work with basalt when it is dense enough. It will be black and probably have visible dots of other minerals in it and take a nice shine. Because basalt can be light and fluffy as Scoria and goes on a scale to very dense, it doesn’t have a Mohs scale number.  

Full disclosure: Some of the information in this blog post appeared earlier in an article I wrote for  Rock & Gem Magazine. I took the pictures of the Volcanic Bomb and Pele's Hair at the Lyman Museum where I took a whole lot of pictures for the upcoming R&G article.

Show Season is in full swing now. Don't miss the chance to see and acquire amazing specimens, slabs, and rough!  Send me a picture of your favorite!

Until next time, Your Lapidary Whisperer,


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