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Gemstones, Minerals & Fossils
Gemstones and Minerals
Wash layer/newb questions
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<blockquote data-quote="Lefty" data-source="post: 449644" data-attributes="member: 2976"><p>The following is from my experience only on the central QLD sapphire fields - and surface digging at that, I never mined underground.</p><p></p><p>Corundum with it's relatively high SG (along with the zircons which are heavier again) tends to sink to the bottom of a steam or gully as it gets washed along. Presumably, many stones have been exposed, washed along and re-buried multiple times. The wash often appears as Goldirocks describes, an alluival gravel made up heavily of water-worn quartz pebbles and other stream worn stones, iron stone pebbles, quartzite boulders can often be present here.</p><p></p><p>Corundum (if it's actually present) will often be concentrated toward the bottom of the layer - in this case, it often rests on a base of hard clay. The stones may be embedded in the top of the clay "floor". Old sapphire miners told me to always be sure to scrape the top couple of inches of the floor as the heavy stones can sink into it.</p><p></p><p>They don;t just keep sinking to eternity despite their weight. In some places on the CQ field, they have discovered as may as four wash layers, all bearing sapphires.</p><p></p><p>Really, your typical surface wash layer is similar to a pulsator tray or gold sluice - the heavies go to the bottom. As stated, that is often a floor of hard clay. Be sure to take the top couple of inches of that clay.</p></blockquote><p></p>
[QUOTE="Lefty, post: 449644, member: 2976"] The following is from my experience only on the central QLD sapphire fields - and surface digging at that, I never mined underground. Corundum with it's relatively high SG (along with the zircons which are heavier again) tends to sink to the bottom of a steam or gully as it gets washed along. Presumably, many stones have been exposed, washed along and re-buried multiple times. The wash often appears as Goldirocks describes, an alluival gravel made up heavily of water-worn quartz pebbles and other stream worn stones, iron stone pebbles, quartzite boulders can often be present here. Corundum (if it's actually present) will often be concentrated toward the bottom of the layer - in this case, it often rests on a base of hard clay. The stones may be embedded in the top of the clay "floor". Old sapphire miners told me to always be sure to scrape the top couple of inches of the floor as the heavy stones can sink into it. They don;t just keep sinking to eternity despite their weight. In some places on the CQ field, they have discovered as may as four wash layers, all bearing sapphires. Really, your typical surface wash layer is similar to a pulsator tray or gold sluice - the heavies go to the bottom. As stated, that is often a floor of hard clay. Be sure to take the top couple of inches of that clay. [/QUOTE]
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Gemstones, Minerals & Fossils
Gemstones and Minerals
Wash layer/newb questions
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