The following table lists ALL radioactive nuclei with a half-life greater than 1000 years.
An element decays away below detectable levels in about ten to fifteen half-lives.
| Isotope | Half-life (yr) | Rel. Abundance |
| Holmium-166m | 1,200 | none |
| Berkelium-247 | 1,380 | none |
| Radium-226 | 1,600 | trace |
| Molybdenum-93 | 4,000 | none |
| Holmium-153 | 4,570 | none |
| Curium-246 | 4,730 | none |
| Carbon-14 | 5,730 | trace |
| Plutonium-240 | 6,563 | none |
| Thorium-229 | 7,340 | none |
| Americium-243 | 7,370 | none |
| Curium-245 | 8,500 | none |
| Curium-250 | 9,000 | none |
| Tin-126 | 10,000 | none |
| Niobium-94 | 20,300 | none |
| Plutonium-239 | 24,110 | none |
| Protactinium-231 | 32,760 | trace |
| Lead-202 | 52,500 | none |
| Lanthanum-137 | 60,000 | none |
| Thorium-230 | 75,380 | none |
| Nickel-59 | 76,000 | none |
| Thorium-230 | 77,000 | trace |
| Calcium-41 | 103,000 | none |
| Neptunium-236 | 154,000 | none |
| Uranium-233 | 159,200 | none |
| Rhenium-186m | 200,000 | none |
| Technetium-99 | 211,000 | none |
| Krypton-81 | 229,000 | none |
| Uranium-234 | 245,500 | trace |
| Chlorine-36 | 301,000 | none |
| Curium-248 | 340,000 | none |
| Bismuth-208 | 368,000 | none |
| Plutonium-242 | 373,300 | none |
| Aluminum-26 | 717,000 | none |
| Selenium-79 | 1,130,000 | none |
| Iron-60 | 1,500,000 | none |
| Beryllium-10 | 1,510,000 | none |
| Zircon-93 | 1,530,000 | none |
| Curium-247 | 1,560,000 | none |
| Gadolinium-150 | 1,790,000 | none |
| Neptunium-237 | 2,144,000 | none |
| Cesium-135 | 2,300,000 | none |
| Technetium-97 | 2,600,000 | none |
| Dysprosium-154 | 3,000,000 | none |
| Bismuth-210m | 3,040,000 | none |
| Manganese-53 | 3,740,000 | none |
| Technetium-98 | 4,200,000 | none |
| Palladium-107 | 6,500,000 | none |
| Hafnium-182 | 9,000,000 | none |
| Lead-205 | 15,300,000 | none |
| Curium-247 | 15,600,000 | none |
| Iodine-129 | 17,000,000 | trace |
| Uranium-236 | 23,420,000 | none |
| Niobium-92 | 34,700,000 | none |
| Plutonium-244 | 80,800,000 | none |
| Samarium-146 | 103,000,000 | none |
| Uranium-236 | 234,200,000 | none |
| Uranium-235 | 703,800,000 | rare |
| Potassium-40 | 1,280,000,000 | rare |
| Uranium-238 | 4,468,000,000 | common |
| Rubidium-87 | 4,750,000,000 | common |
| Thorium-232 | 14,100,000,000 | common |
| Lutetium-176 | 37,800,000,000 | rare |
| Rhenium-187 | 43,500,000,000 | common |
| Lanthanum-138 | 105,000,000,000 | rare |
| Samarium-147 | 106,000,000,000 | common |
| Platinum-190 | 650,000,000,000 | rare |
| Tellurium-123 | >1 x 10^13 | rare |
| Osmium-184 | >5.6 x 10^13 | rare |
| Gadolinium-152 | 1.08 x 10^14 | rare |
| Tantalum-180m | >1.2 x 10^15 | rare |
| Xenon-124 | >1.6 x 10^14 | rare |
| Indium-115 | 4.41 x 10^14 | common |
| Zinc-70 | >5 x 10^14 | rare |
| Hafnium-174 | 2.0 x 10^15 | rare |
| Osmium-186 | 2.0 x 10^15 | common |
| Samarium-149 | >2 x 10^15 | common |
| Neodymium-144 | 2.29 x 10^15 | common |
| Samarium-148 | 7 x 10^15 | common |
| Cadmium-113 | 7.7 x 10^15 | common |
| Cerium-142 | >5 x 10^16 | common |
| Tungsten-183 | >1.1 x 10^17 | common |
| Vanadium-50 | 1.4 x 10^17 | rare |
| Lead-204 | 1.4 x 10^17 | common |
| Chromium-50 | >1.8 x 10^17 | common |
| Tungsten-184 | >3 x 10^17 | common |
| Calcium-48 | >6.3 x 10^18 | common |
| Molybdenum-100 | 1.0 x 10^19 | common |
| Neodynium-150 | >1.1 x 10^19 | common |
| Zircon-96 | >3.8 x 10^19 | common |
| Selenium-82 | 1.1 x 10^20 | common |
| Tellurium-130 | 7.9 x 10^20 | common |
| Xenon-136 | >2.4 x 10^21 | common |
| Tellurium-128 | 2.2 x 10^24 | common |
| Stable Isotopes | infinite | ** |
* "Common" means the isotope comprises more than 1% of the local atomic abundance
of its element. "Rare" means it has an abundance of less than 1%. "Trace" means
the elements concentration is effectively negligible, much less than 0.01%.
In the case of Protactinium (whose only isotope is radioactive and short-lived)
the concentration was compared to that of nearby elements.
**Of 280 total stable isotopes, about 70% are common, 30% are rare, and 1% are trace.
NO stable isotopes are absent.
Sources:
http://ie.lbl.gov/toi/nucSearch.asp
http://www.webelements.com/
http://www.blackcatsystems.com/science/natRadiation.html
Serway et al. 1997, "Modern Physics"