VOLUME 44, NO. 1 J ANUARY 2009
GYPSUM MEETING BY D EAN S AKABE Wednesday To start the New Year, we will be high sions. (1) Please note that the term January 28 lighting rather industrial mineral: Gyp “Desert Rose” also applies to rosette sum. Gypsum, a Hydrated Calcium Sul shaped Barite with sand inclusions, so 7:00—9:00 pm fate, is one of the more common miner these are two different minerals and Makiki District als in sedimentary environments. It is a should not be confused with each other. Park major rock forming mineral that pro Administration duces massive beds, usually from pre cipitation out of highly saline waters. Building Gypsum can have many inclusions of other minerals and even trapped bubbles NEXT MONTH of air and water. TBD Gypsum crystals can be colorless and transparent, despite being used in the LAPIDARY white drywall we are all familiar with. Gypsum is also a natural insulator, and it feels warm to the touch when compared Every Thursday to a more ordinary rock or quartz crys 7pm 9pm tal. Sheets of clear crystals can be easily Second floor Arts peeled from a larger specimen. and Crafts Bldg Plaster of Paris is made by heating gyp Makiki District sum to about 300 degrees Fahrenheit, Park driving 75% of the water out of the (1) Desert Rose mineral. This reaction absorbs energy, enabling a sheet of drywall to resist fire As one of the club members once told for a while. If Gypsum were heated fur me they collected Selenite spars from MEMBERSHIP ther to about 350 degrees F, the remain Kalama valley. When Kalama valley was COSTS ing water is driven out, and it converts developed into houses, the excess dirt 2008 into the mineral anhydrite. was trucked off and dumped around (for lack of knowing the right name) Gypsum can form in sandy areas, and Makapuu, the area on the other side of Single: $10.00 when forming, the crystals sometimes the road from Hawaii Kai Golf Course. Family: $15.00 trap sand inside causing the specimen to Digging in this area, especially after all become brown and opaque. These sand of the rain we have been having, Selenite inclusions sometimes form hourglass rosettes can be found . formations in a crystal. They are also present in “Desert Roses”, which are rosette shaped Gypsum with sand inclu Rock and Mineral Society of Hawai‛i INC. Gypsum, page 2
These specimens can be small and A fine grained massive material is . fragile, and should only be cleaned called alabaster and is an ornamental only with water. Soaps and deter stone used for centuries in fine carv gents should not be used; they enter ings. It is thought that the first uses cracks and crevices of a crystal, de of gypsum were for sculptures. Ala stroying its luster. Ultrasonic clean baster is a soft solid form of gypsum ers filled with water work great with that takes carvings well thus it was rosettes. able to be carved into many differ ently shaped objects. (2) Blocky crystal habit Other crystal habits include the tabu lar, bladed, or blocky crystals with a Gypsum crystals can be extremely slanted parallelogram outline. The large among the largest on the en pinacoid faces dominate with jutting tire planet. A cave in Naica, Mexico, prism faces on the edges of the tabu The Cave of Swords, contains crys lar crystals (2). Long thin crystals tals that dwarf the people inside (5). show bends and some specimens The ideal conditions for the slow bend into spirals called “Ram's Horn growth of gypsum were maintained Selenite.” (3) for thousands of years, allowing a (3) Ram’s Horn Se few crystals to grow to enormous lenite. There are two types of twinning. sizes. At Pilar de Jarravia, Spain, One produces the shorter “spear there is a gypsum, geode currently head twin” or “swallowtail twin.” thought of as the largest geode in the The other type produces a potentially world. larger “fishtail twin”. Gypsum has several varietal names that are widely used in the mineral trade: Selenite is the colorless and transpar (4) Selenite ent variety that shows a pearl like luster and has been described as hav ing a moon like glow (4). The word selenite comes from the Greek for Moon and means “moon rock”. Se lenite was used for windows before glass was created. It contains a large amount of water, and this gives it fire protection qualities. Another variety is a compact fiber ous aggregate called satin spar . This variety has a very satin like look that (5) Giant gypsum crys gives a play of light up and down the tals up to 12 m, Naica fibrous crystals. mine, Mexico Rock and Mineral Society of Hawai‛i INC. Rock & Mineral News and Notes, page 3 Society of Hawai `i, Inc.
2008 Officers DOOR PRIZES President Please note that we have instituted door prize drawings at our monthly meet Faye Chambers ings. Because of Hawaii’s gambling laws, these drawings cannot be con 621 6710 ducted in the common “raffle” format where tickets are sold. Rather, each [email protected] paid member attending the meeting will receive a drawing ticket upon request. A voluntary donation of $1.00 is requested and encouraged. Drawings will be Vice President/Admin. conducted at the end of the meeting with available prizes awarded in random Ed Sawada order. You must be present to win. Please remember: if you win a prize, Vice President/Lapidary please bring one to the next meeting. This helps to keep our drawings going. Dean Sakabe Thank you. 535 5012 (day) [email protected] Treasurer WE H AVE A WEBSITE ! Debbie Iijima 539 4552 (day) http://pohakugalore.net/Hui_pohaku/Hiu_pohaku_1.html Recording Secretary MAHALO TO M ARKUS FOR HELPING US GET OUT OF THE ELECTRONIC STONE AGE ! Jade Emory [email protected] Corresponding Secretary Jade Emory [email protected] 429 2411 Newsletter Editor Elise Thomasson [email protected] The Rock & Mineral Society meets on the 4th Wednesday of each month (except for adjusted dates in November and Decem ber) at the Makiki District Park, 7:00 9:00 pm. Enter from Keeaumoku Street. Parking is free but limited. The Newsletter is published monthly, some days prior to the meetings and is distributed in electronic format by email (Adobe Acrobat PDF file at tachment). Printed copies are “snail” mailed to those who do not have email. The electronic format usually contains full Inside a gypsum geode, Pilar de Jarravia, Spain color images; the print version may be limited to B&W due to reproduction costs. ALAN Z EIGLER S INKHOLE DEDICATION ! What wonderful news concerning about the preservation of areas of Any newsletter comments are scientific interest here in Hawai‘i! Since the Hawaiian islands are so appreciated, and can be sent to isolated, the presence of eagles, owls, ducks, and geese in these sink [email protected] holes by Kapolei boat harbor is especially noteworthy. Keith © Rock & Mineral Society of Krueger was pleased to share this news, and to tell that Bill and Hawai `i, Inc. other members of our rock club presented testimony to the city P.O. Box 23020 council. Funds have been set aside of zoning and education. Honolulu, HI 96823 3020 P.O. Box 23020 Honolulu, HI 96823-3020