Melvin Grey / Purple-throated mountain gem (Lampornis calolaemus) adult female - about to feed from flower, Atlantic Rainforest, Costa Rica.

Bence Mate / White-throated Mountain Gem (Lampornis castaneoventris), Green-crowned Brilliant (Heliodoxa jacula) group of three with one in flight, Savegre, Costa Rica

Gerrit Vyn / Male White-throated Mountain Gem (Lampornis castaneoventris). Tamalanca Mountains, Costa Rica. May.

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird female feeding and pollinating flower of epiphytic Heath (Cavendishia melastomoides) cloud forest, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird female feeding at and pollinating epiphytic Orchid flowers (Elleanthus sp), Monteverde Cloud Forest Reserve, Costa Rica

Ernie Janes / Purple-throated mountaingem (Lampornis calolaemus) female Costa Rica.

Ernie Janes / Purple-throated mountain gem hummingbird (Lampornis calolaemus) female, Costa Rica.

Heather Angel / Purple throated mountain gem hummingbird (Lampornis calolaemus) hovering as it nectars on Porterweed (Stachytarpheta frantzii). Costa Rica.

Ernie Janes / Beardtongues (Penstemon) 'Torquay Gem' flowers.

Paul Hobson / Purple-throated mountain-gem (Lampornis calolaemus) nectaring at flower. Costa Rica.

Thomas Marent / Orange-banded Gem (Crocozona coecias) butterfly, Santa Maria, Colombia

Phil Savoie / Purple-throated mountain gem (Lampornis calolaemus), Volcano Pos, Costa Rica.

Phil Savoie / Purple-throated mountain gem (Lampornis calolaemus), Volcano Pos, Costa Rica.

Phil Savoie / Purple-throated mountain gem (Lampornis calolaemus), Volcano Pos, Costa Rica.

Sue Daly / Gem anemones (Aulactinia verrucosa) Isle of Man, July.

Adrian Davies / Common puffball (Lycoperdon perlatum) Sussex, UK, November.

Franco Banfi / Nudibranch (Goniobranchus geminus), Aldabra Atoll, Natural World Heritage Site, Seychelles, Indian Ocean.

TJ Rich / Cutting sapphires using traditional equipment, Ratnapura, Sri Lanka, December 2012.

TJ Rich / Cut, polished and rough sapphires, Sri Lanka.

TJ Rich / Gemstone dealers, China Fort, Beruwela, Sri Lanka, December 2012.

TJ Rich / Sapphire cutting, Ratnapura, Sri Lanka, December 2012.

TJ Rich / Rough gemstones in hand of miner, Ratnapura, Sri Lanka, December 2012.

Steve O. Taylor (GHF) / Miners panning for diamonds in a pool, Kono District, Sierra Leone, 2007.

Steve O. Taylor (GHF) / Miners panning for diamonds in a pool, Kono District, Sierra Leone, 2007.

Steve O. Taylor (GHF) / Miners panning for diamonds in a pool, Kono District, Sierra Leone, 2007.

Ingo Arndt / Purple throated mountain gem {Lampornis calolaema} male feeding at flower, Costa Rica

Mike Read / Common puffball (Lycoperdon perlatum) growing through leaf litter in deciduous woodland near Buckhill Hole, New Forest National Park, Hampshire, England, UK, October 2015.

Bence Mate / White-throated mountain gem hummingbirds (Lampornis castaneoventris) fighting, Savegre, Costa Rica

Paul D Stewart / Ammonite (Placenticeras) shell from upper Cretaceous period 75 million year ago, showing iridescent ammolite gem skin, cracked and flaked in the typical 'dragon skin' pattern.

Andy Sands / Common puffball (Lycoperdon perlatum) releasing spores, Buckinghamshire, England, UK, November. Digital composite.

Andy Sands / Common puffball (Lycoperdon perlatum) Digital composite. Digital composite

Matthew Maran / Common puffball (Lycoperdon perlatum), Hampstead Heath, England, UK. September.

Melvin Grey / White-throated mountain gem hummingbird (Lampornis castaneoventris) hummingbird male perched, Sevegre Valley, Costa Rica.

Melvin Grey / Purple-throated mountain gem hummingbird (Lampornis calolaemus) hummingbird adult female in flight, Atlantic Rainforest, Costa Rica.

Melvin Grey / Purple-throated mountain gem hummingbird (Lampornis calolaemus) hummingbird adult female on nest, Costa Rica.

Pete Oxford / Gem anole (Anolis gemmosus) Mindo Cloud Forest, Western slopes, Andes, Ecuador.

Pete Oxford / Gem anole (Anolis gemmosus) Mindo Cloud Forest, Western slopes, Andes, Ecuador.

Doug Wechsler / Warted Puffball (Lycoperdon perlatum) Larrabee State Park, Whatcom County, Washington, USA, September.

Floris van Breugel / Autumn colors of plants showing through an early winter snowfall in Alpine Lakes wilderness, with Kalteen Peak and Gem Lake, Washington, USA, October 2013.

Floris van Breugel / Tent lit up at night after an early winter snowfall, with Kaleetan Peak and Gem Lake, near Snoqualmie Pass, Cascades, in Washington, USA, October 2013.

Glenn Bartley / Variable Mountain-gem (Lampornis castaneoventris) female, Costa Rica

E.J. Peiker / Purple-throated Mountain-gem (Lampornis calolaemus) female feeding on nectar, Costa Rica

E.J. Peiker / White-bellied Mountain Gem (Oreopyra hemileucus) feeding on nectar, Costa Rica

E.J. Peiker / White-bellied Mountain Gem (Oreopyra hemileucus), Costa Rica

E.J. Peiker / Purple-throated Mountain-gem (Lampornis calolaemus) female, Costa Rica

E.J. Peiker / Purple-throated Mountain-gem (Lampornis calolaemus) female feeding on nectar at flower, Costa Rica

Glenn Bartley / White-bellied Mountain Gem (Oreopyra hemileucus) feeding on nectar, Costa Rica

Bence Mate / Portrait of Purple-throated mountain-gem (Lampornis calolaema) perching on branch, Costa Rica

Bence Mate / Green crowned brilliant (Heliodoxa jacula) and Purple throated mountain-gem (Lampornis calolaema) perching on branch, Costa Rica,

Bence Mate / Purple-throated mountain-gem hummingbird (Lampornis calolaema) on hand-held feeder, Costa Rica

Bence Mate / Purple-throated mountain-gem hummingbird (Lampornis calolaema) in flight, Costa Rica

Bence Mate / Head portrait of Purple-throated mountain-gem hummingbird (Lampornis calolaema) Costa Rica

Bence Mate / Two Green crowned brilliant hummingbirds (Heliodoxa jacula) and Purple throated mountain-gem hummingbird (Lampornis calolaema) perched on branch, Costa Rica

Bence Mate / Green crowned brilliant hummingbird (Heliodoxa jacula) and Purple throated mountain-gem hummingbird (Lampornis calolaema) perching on branch, Costa Rica

Sue Daly / Gem Nudibranch (Dendrodoris krusensternii) Poor Knights Islands, New Zealand, February

Ben Lascelles / White-throated Mountain Gem (Lampornis castaneoventris). Los Quetzales, Chiriqui, Panama.

Kim Taylor / Grey-tailed mountain-gem (Lampornis castaneoventris cinereicauda) female perched, Costa Rica

Konrad Wothe / Purple throated Mountain gem (Lampornis castaneoventris cinereicauda) female drinking on flower, Cerro de la Muerte, Costa Rica

Roland Seitre / White-throated Mountain-gem Hummingbird (Lampornis castaneoventris). Savegre, Cerro de la Muerte, Costa Rica.

Steve Gettle / Variable Mountain-gem (Lampornis castaneoventris) hummingbird, Costa Rica

Steve Gettle / Variable Mountain-gem (Lampornis castaneoventris) hummingbird, Costa Rica

Alex Hyde / Wartlet / Gem Anemone (Bunodactis verrucosa) in rockpool, with mouth parts visible, Pembrokeshire, Wales, UK. July.

Gerrit Vyn / White-throated Mountain Gem Hummingbird(Lampornis castaneoventris) female, perched on green vegetation, Tamalanca Mountains, Costa Rica. May.

Philippe Clement / Common / gem-studded puffballs / devil's snuff-box (Lycoperdon perlatum / gemmatum) Belgium

Stephen Dalton / Grey tailed mountain gem hummingbird (Lampornis castaneoventris) perched, Costa Rica

Stephen Dalton / Grey tailed mountain gem hummingbird (Lampornis castaneoventris) perched, Costa Rica

Stephen Dalton / Grey tailed mountain gem hummingbird (Lampornis castaneoventris) perched, Costa Rica

Merryn Thomas / Gem stones for sale in the Atlas Mountains, Morocco, November 2008.

Philippe Clement / Common / gem-studded puffball (Lycoperdon perlatum / gemmatum) among fallen beech leaves, Belgium

Philippe Clement / Common / gem-studded puffball (Lycoperdon perlatum / gemmatum) among fallen beech leaves, Belgium

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male at flowers, Monteverde Cloud Forest, Costa Rica

Gary K. Smith / Lettuce, 'Little Gem' variety {Lactuca sativa} being grown in an old compost bag filled with garden compost on an urban patio, UK, August

Thomas Marent / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird female, Costa Rica

Edwin Giesbers / Purple throated mountain gem (Lampornis calolaema) perched on branch, Costa Rica

Tim Fitzharris / Grey-tailed Mountain Gem (Lampornis cinereicauda) hummingbird male foraging, Costa Rica

Tim Fitzharris / Grey-tailed Mountain Gem (Lampornis cinereicauda) hummingbird female foraging, Costa Rica

Tim Fitzharris / Grey-tailed Mountain Gem (Lampornis cinereicauda) hummingbird female foraging, Costa Rica

Gary K. Smith / Sowing Lettuce seeds {Lactuca sativa} ' Little Gem' variety, in vegetable plot, UK

Konrad Wothe / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird female feeding, Cerro de la Muerte, Costa Rica

Konrad Wothe / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male feeding, Cerro de la Muerte, Costa Rica

Konrad Wothe / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird female feeding, Cerro de la Muerte, Costa Rica

Rolf Nussbaumer / Purple-throated Mountain-gem {Lampornis calolaema} male perched, Central Valley, Costa Rica

Rolf Nussbaumer / Purple-throated Mountain-gem {Lampornis calolaema} male perched on Banana flower, Central Valley, Costa Rica

Rolf Nussbaumer / Purple-throated Mountain-gem {Lampornis calolaema} male feeding from Ginger flower, Central Valley, Costa Rica

Rolf Nussbaumer / Purple-throated Mountain-gem {Lampornis calolaema} male feeding from flower, Central Valley, Costa Rica

Rolf Nussbaumer / Purple-throated Mountain-gem {Lampornis calolaema} male feeding from Banana flower, Central Valley, Costa Rica

Ingo Arndt / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird drinking nectar, Monte Verde, Costa Rica

Fabio Liverani / Purple throated mountain gem {Lampornis calolaema} Monteverde NR, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male flying, Monteverde Cloud Forest Reserve, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male flying, Monteverde Cloud Forest Reserve, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird feeding on and pollinating Heath (Cavendishia bracteata) flowers, cloud forest, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male, feeding and pollinating flowers, epiphytic Heath (Cavendishia complectens) cloud forest, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male, cloud forest, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird feeding and pollinating flowers of epiphytic Heath (Cavendishia complectens) cloud forest, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird male perching with wings spread, Monteverde Cloud Forest Reserve, Costa Rica

Michael & Patricia Fogden / Purple-throated Mountain-gem (Lampornis calolaemus) hummingbird female feeding and pollinating flower of epiphytic One-day Orchid (Sobralia amabilis) cloud forest, Costa Rica