Indonesian Gemstone Promotion Center

Mengenal Tektit

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Martes 04 de Noviembre de 2008 13:22

Tektit adalah batuan kecil berwarna hitam yang tersusun dari gelas silikat dan dipercaya sebagai meteorit yang datang dari luar angkasa atau extra-terrestrial. Beberapa ahli berpendapat bahwa tektit adalah serpihan batu bulan yang terlempar akibat benturan dahsyat dari benda-benda besar yang jatuh ke permukaannya. Beberapa ahli lain berpendapat bahwa tektit adalah pecahan dari meteorit besar yang saling berbenturan yang pecahannya masuk ke atmosfir bumi berupa benda-benda meleleh (tektit = tektos = melted = meleleh).

Lokasi ditemukannya tektit tersebar di daerah-daerah tertentu misalnya Australia dan Tasmania (australites), Texas (bediasites), Indo-Cina (indochinites), Malaysia (malaysianites), Checoslovakia (moldavites), Luzon (philipinites atau rizalites) , Billiton (billitonites = batu satam), Martapura (batu kelulut), Jawa Tengah ( avanites = batu meteor), dan lain-lain.

Umur tektit ketika sampai di permukaan bumi berbeda-beda. Dengan metode kalium argon, tektik Amerika Utara ditafsir berumur sekitar 34 juta tahun, Chekoslovakia sekitar 14,8 juta tahun, Indo-Cina, Indonesia dan Australia sekitar 600-700 tahun.

Bentuk dan rupa tektit sangat dipengaruhi oleh mekanisme pembentukan dan proses erosi yang mengikutinya. Kecepatan gerak dan derajat rotasi pada waktu tektit menembus atmosfir bumi atau terlempar akibat benturan dengan permukaan bumi menyebabkan bentuk tektit sangat beragam misalnya bundar, lonjong, tear drop, buah pir, halter, tidak beraturan dengan lobang pelepasan gas berukuran besar, atau dengan goresan atau alur-alur tertentu (lihat foto di bawah). Permukaan tektit juga menunjukkan beragam rupa dan corak. Hal ini sangat dipengaruhi oleh proses geologi yang dialaminya sejak pembentukannya sampai tiba di tempat ditemukannya.

Ultima actualización ( Jueves 21 de Enero de 2010 09:53 )

What Jasper Is?

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Miércoles 31 de Diciembre de 2008 15:49

Introduction

Jasper is derived from the Greek for "spotted stone". Jasper is usually considered a chalcedony, but put by scientists in a group by itself because of its grainy structure. The finely grained, dense jasper contains up to twenty percent foreign materials that determine its color, streak and appearance. Uniform jasper is rare. It usually is multicolored, striped spotted or flamed.
Some of the most treasured gems are those that show a picture that appears to be taken from nature, called "landscapes". Oregon's Biggs Jasper is now the most common source. Another specialty is bloodstone or blood jasper, also known as "heliotrope", a dark green chalcedony or jasper with flecks of red. Bloodstone is the Zodiac birthstone for Aries.

Ultima actualización ( Jueves 22 de Octubre de 2009 15:59 )

Gemstone Hardness

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Miércoles 31 de Diciembre de 2008 15:59

Mohs' scale of mineral hardness was created by the German mineralogist Friedrich Mohs in 1822 to measure the relative hardness or scratch resistance of various minerals. He based it on ten readily available minerals. As it is an ordinal scale, you have to compare two minerals to decide which is harder. The scale is neither linear nor logarithmic. For example, corundum is twice as hard as topaz, but diamond is almost four times as hard as corundum.

The hardness of a material is measured against the scale by finding the hardest material that that the given material can scratch, or the softest material that can scratch the given material.

Mohs original scale is as follows:

Ultima actualización ( Jueves 22 de Octubre de 2009 16:01 )

Birthstone

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Miércoles 31 de Diciembre de 2008 16:04

Birthstones, Zodiac and Anniversary Stones

Birthstones are of special interest to gemstone lovers and the association of specific gemstones with months of the year goes back centuries. As the famous gemologist G.F. Kunz noted in his book, The Curious Lore of Precious Stones, "There is no doubt that the owner of a ring or ornament set with a birthstone is impressed with the idea of possessing something more intimately associated with his or her personality than any other stone, however beautiful or costly. The idea that birthstones possess a certain indefinable, but nonetheless real significance has long been present and still holds a spell over the minds of all who are gifted with a touch of imagination and romance."

Ultima actualización ( Jueves 22 de Octubre de 2009 16:00 )

The History of Birthstones

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Miércoles 31 de Diciembre de 2008 16:08

The idea of birthstones -- a gemstone assigned to each month of the year -- is thought to be an ancient one, and scholars trace it back to the Breastplate of Aaron described in the Bible in the book of Exodus. The Breastplate was a religious garment set with twelve gemstones that represented the twelve tribes of Israel. The gems were set in four rows of three: sardius, topaz and carbuncle; emerald, sapphire and diamond; ligure, agate and amethyst; and beryl, onyx and jasper.

So how did we get from gemstones representing the twelve tribes of Israel to birthstones? The writings of Flavius Josephus (1st century AD) and St. Jerome (fifth century AD) made the connection between the 12 stones in the

Ultima actualización ( Jueves 22 de Octubre de 2009 16:04 )

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