STONE DICTIONARY

    CHERT

    A rock formed from the accumulation of dead organisms, such as radiolarian, that existed during the Cambrian period of the Paleozoic era. Exceptionally hard due to being compacted at the bottom of the deep sea.

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    ひすい

    JADE

    A rock formed from the accumulation of fine-grained jadeite and pyroxene. Hard varieties are called jadeite, while softer ones are known as nephrite. It has been processed and utilized for jewelry and daily goods since ancient times.

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    かんらんせき

    OLIVINE

    The mineral that dominates much of the uppermost part of the Earth's mantle. Emitting a melting-like olive-colored luster, it is known as peridot and is the birthstone for August.

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    あんざんがん

    ANDESITE

    A rock formed by the rapid solidification of magma at the Earth's surface. It consists of both slowly crystallized portions and quickly cooled segments, creating a porphyritic texture. The name 'andesite' originates from the abundant deposits found in the Andes Mountains of South America.

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    りゅうもんがん

    RHYOLITE

    A rock formed by the rapid cooling and solidification of magma at or near the Earth's surface. Its name derives from the flowing patterns of magma that appear during this process.

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    めのう

    AGATE

    A mineral formed by the overlapping of layers of quartz or opal. The opaque variety is called chalcedony, while those with striped patterns or semi-transparency are called agate. It is one of the Seven Treasures in Buddhism.

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    せっかいがん

    LIMESTONE

    A rock formed from the accumulation of remains such as coral, foraminifera, and shells, which inhabited tropical seas from the Ordovician period to the Middle Ages, around the Cretaceous period. It may contain fossils of trilobites and shells. In ancient times, it was used in the construction of Egyptian pyramids, and today it is used as a material for concrete and fertilizer.

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    じゃもんがん

    SERPENTINE

    A rock formed deep underground when water mixes with olivine. Named for its surface pattern resembling snakeskin. Due to its tendency to fracture easily, areas with abundant serpentine rocks are prone to landslides.

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    げんぶがん

    BASALT

    A rock formed by the rapid cooling of magma. Its chemical composition is similar to mantle material. Fresh specimens are black, but they can turn reddish-brown as iron content oxidizes. Basalt forms the ocean floor worldwide and makes up volcanic regions such as Hawaii and Iceland.

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    せきえいはんがん

    石英斑岩

    石英（クオーツ）の結晶が多く散りばめられていてキラキラと細かく光る。

    マグマが比較的浅めの地下で固まった岩。

    含まれる鉄分が酸化して綺麗な模様が浮かぶことがある。

    中でも姫川薬石（ひめかわやくせき）と呼ばれるものは新潟県糸魚川市と富山県の一部でしか産出されず、こちらは鉱物。弱イオンやラジウムを放出しているため自己治癒力や集中力を高める効果があるとされている。

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    かこうがん

    花崗岩

    地下深くでマグマがゆっくりと固まってできた岩石。

    白色〜白灰色で黒い粒が散りばめられている。

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    そうちょうがん

    曹長岩

    翡翠に似ているが、翡翠より軽くて透明感が少ない。
    白色や白灰色で模様がないものが多い。

    → Collecting Spot

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    火成岩

    変成岩

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